The effect of local cortical microfilament disorganization on ooplasmic segregation in the loach (Misgurnus fossilis) egg

Ivanenkov, Vasily V.; Minin, A. A.; Meshcheryakov, Viktor; Martynova, Larisa E.

doi:10.1016/0045-6039(87)90410-6

Cited by 17 publications

(6 citation statements)

References 18 publications

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“…2). Our inhibitor‐based observations are supported by similar reports from zebrafish ( Katow 1983; incubation in cytochalasin B) and loach ( Ivanenkov et al 1987 ; injection of cytochalasin D), whereas, in the medaka zygote, both MF and MT appear to be involved in its bipolar segregation ( Abraham et al 1993 ; Webb et al 1995 ; incubated in cytochalasin D and colchicine). We propose therefore that the band of elevated calcium demonstrated by Leung et al (1998) is organizing and modulating an actin MF‐based surface contraction in the animal hemisphere cortex.…”

Section: Discussionsupporting

confidence: 88%

“…The present observations are therefore at odds with the long‐held idea that the force‐generating mechanism for segregation in zebrafish resides in the vegetal hemisphere ( Lewis & Roosen‐Runge 1942, 1943; Hisaoka & Firlit 1960; Beams & Kessel 1976; Katow 1983; Beams et al 1985 ). Our placement of the force‐generating mechanism in the animal hemisphere is, however, supported by Ivanenkov et al (1987) , who demonstrated that in the loach, ooplasmic segregation could be suppressed by local disorganization of the MF network at the animal but not the vegetal hemisphere.…”

Section: Discussionsupporting

confidence: 67%

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On the mechanism of ooplasmic segregation in single‐cell zebrafish embryos

2000

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It has been previously shown that localized elevations of free cytosolic calcium are associated with a morphological contraction in the forming blastodisc and animal hemisphere cortex during ooplasmic segregation in zebrafish zygotes. It was subsequently proposed, in a hypothetical model, that these calcium transients might be linked to the contraction of a cortically located actin microfilament network as a potential driving force for segregation. Here, by labeling single-cell embryos during the major phase of segregation with rhodamine-phalloidin, direct evidence is presented to indicate that the surface contraction was generated by an actin-based cortical network. Furthermore, while zygotes incubated with colchicine underwent normal ooplasmic segregation, those incubated with cytochalasin B did not generate a constriction band or segregate to form a blastodisc. During segregation at the single-cell stage, ooplasm simultaneously moved in two directions: toward the blastodisc within the so-called axial streamers, and toward the vegetal pole in the peripheral ooplasm. The velocities of both axial and peripheral streaming movements are reported. By injection of a fluorescein isothiocyanate (FITC)-labeled 2000 kDa dextran into the peripheral ooplasm it was demonstrated that a portion of it feeds into the bases of the extending streamers, which helps to explain the lack of accumulation of ooplasm at the vegetal pole. These new data were incorporated into the original model to link the bipolar ooplasmic movements with the calcium-modulated, actin-mediated contraction of the animal hemisphere cortex as a means of establishing and driving ooplasmic segregation in zebrafish.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 67%

On the mechanism of ooplasmic segregation in single‐cell zebrafish embryos

2000

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“…Cortical granules (CG) release their contents at the egg cortex, contributing to chorion expansion and surface remodeling (Fuentes and Fernandez, 2010;Hart, 1990;Tsaadon et al, 2006;Wong and Wessel, 2006). Stabilizing or destabilizing F-actin established the dependence of both CGE and cytoplasmic streaming on a dynamic actin cytoskeleton (Becker and Hart, 1999;Fernandez et al, 2006;Hart and Fluck, 1996;Ivanenkov et al, 1987;Leung et al, 2000;Wolenski and Hart, 1988). Maternally deposited dorsal determinants (DDs), including wnt8a mRNA, reside at the vegetal pole (Kosaka et al, 2007;Lu et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Dachsous1b cadherin regulates actin and microtubule cytoskeleton during early zebrafish embryogenesis

et al. 2015

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Dachsous (Dchs), an atypical cadherin, is an evolutionarily conserved regulator of planar cell polarity, tissue size, and cell adhesion. In humans, DCHS1 mutations cause pleiotropic Van Maldergem syndrome. Here, we report that mutations in zebrafish dchs1b and dchs2 disrupt several aspects of embryogenesis, including gastrulation. Unexpectedly, maternal zygotic (MZ) dchs1b mutants show defects in the earliest developmental stage, egg activation, including abnormal cortical granule exocytosis (CGE), cytoplasmic segregation, cleavages, and maternal mRNA translocation, in transcriptionally quiescent embryos. Later, MZdchs1b mutants exhibit altered dorsal organizer and mesendodermal gene expression, due to impaired dorsal determinant transport and Nodal signaling. Mechanistically, MZdchs1b phenotypes can be explained in part by defective actin or microtubule networks, which appear bundled in mutants. Accordingly, disruption of actin cytoskeleton in wild-type embryos phenocopied MZdchs1b mutant defects in cytoplasmic segregation and CGE. Whereas, interfering with microtubules in wild-type embryos impaired dorsal organizer and mesodermal gene expression without perceptible earlier phenotypes. Moreover, the bundled microtubule phenotype was partially rescued by expressing either full-length Dchs1b or its intracellular domain, suggesting Dchs1b affects microtubules and some developmental processes independent of its known ligand Fat. Our results indicate novel roles for vertebrate Dchs in actin and microtubule cytoskeleton regulation in the unanticipated context of the single-celled embryo.

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“…Studies on other types of eggs also suggest an important role of (cortical) cytoskeletal structures in the localization of morphogenetic factors (see e.g. Arnold and Williams-Arnold 1974;Reverberi 1975;Osanai 1981, 1985;Eckberg and Kang 1981 ;Jeffery and Meier 1983;Shimizu 1986Shimizu , 1988Ivanenkov 1987;Sardet et al 1988a), and possibly also in the localization of maternal mRNAs (Jeffery 1984;Jeffery et al, 1986;Yisraeli and Melton 1988;Pondel and King 1988). Finally, it has been suggested that cortical microtubules are involved in specifying the dorso-ventral axis in the frog embryo (Elinson and Rowning 1988).…”

Section: Introductionmentioning

confidence: 92%

The ultrastructural organization of the isolated cortex in eggs ofNassarius reticulatus (Mollusca)

Speksnijder

Jong

Wisselaar

et al. 1989

Roux’s Arch Dev Biol

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We have studied the organization of the cortex in fertilized eggs ofNassarius reticulatus by examining rotary-shadowed whole mounts of isolated cortices in the transmission electron microscope. The following components were distinguished: (a) the plasma membrane, with clathrin-coated areas and coated pits, (b) microfilaments and microtubules, and (c) a tubulovesicular network of endoplasmic reticulum. Microfilaments were identified by labeling with heavy meromyosin, and microtubules with a monoclonal anti-tubulin antibody, using both immunofluorescence microscopy and immunogold labeling for transmission electron microscopy. The microfilaments are organized in a network parallel to and closely associated with the plasma membrane, with typical Y- and X-shaped intersections. The endoplasmic reticulum is associated with this microfilamentous lattice. The microtubules also run parallel to the plasma membrane, but they are located at a greater distance, as can be inferred from stereo images. In the uncleaved egg, numerous microtubules are present in the egg cortex. Shortly before polar lobe formation, at the onset of mitosis, the microtubules disappear almost entirely. They reappear again at the end of first cleavage, as the polar lobe is being resorbed. The synthesis of cortical microtubules at this stage appears to depend on the presence of microtubule-organizing centers in the animal hemisphere of the egg, since microtubules do not reappear in isolated polar lobes. Clathrin-coated areas are present in both the animal and vegetal hemisphere before polar lobe formation. During mitosis, the clathrin-coated plaques and pits are found almost exclusively in the animal hemisphere. After resorption of the polar lobe, at the two-cell stage, no clathrin-coated areas were found at all.

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The effect of local cortical microfilament disorganization on ooplasmic segregation in the loach (Misgurnus fossilis) egg

Cited by 17 publications

References 18 publications

On the mechanism of ooplasmic segregation in single‐cell zebrafish embryos

On the mechanism of ooplasmic segregation in single‐cell zebrafish embryos

Dachsous1b cadherin regulates actin and microtubule cytoskeleton during early zebrafish embryogenesis

The ultrastructural organization of the isolated cortex in eggs ofNassarius reticulatus (Mollusca)

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