scholarly journals Evidence for the involvement of microtubules, ER, and kinesin in the cortical rotation of fertilized frog eggs.

1991 ◽  
Vol 114 (5) ◽  
pp. 1017-1028 ◽  
Author(s):  
E Houliston ◽  
R P Elinson
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Sea Urchin ◽  
Rana Pipiens ◽  
Cortical Microtubules ◽  
Cell Biol ◽  
Vegetal Cortex ◽  
Almost All ◽  
Cytoplasmic Side ◽  
Cytokeratin Filaments

During the first cell cycle, the vegetal cortex of the fertilized frog egg is translocated over the cytoplasm. This process of cortical rotation creates regional cytoplasmic differences important in later development, and appears to involve an array of aligned microtubules that forms transiently beneath the vegetal cortex. We have investigated how these microtubules might be involved in generating movement by analyzing isolated cortices and sections of Xenopus laevis and Rana pipiens eggs. First, the polarity of the cortical microtubules was determined using the "hook" assay. Almost all microtubules had their plus ends pointing in the direction of cortical rotation. Secondly, the association of microtubules with other cytoplasmic elements was examined. Immunofluorescence revealed that cytokeratin filaments coalign with the microtubules. The timing of their appearance and their position on the cytoplasmic side of the microtubules suggested that they are not involved directly in generating movement. ER was visualized with the dye DiIC16(3) and by immunofluorescence with anti-BiP (Bole, D. G., L. M. Hendershot, and J. F. Kearney, 1986. J. Cell Biol. 102:1558-1566). One layer of ER was found closely underlying the plasma membrane at all times. An additional, deeper layer formed in association with the microtubules of the array. Antibodies to sea urchin kinesin (Ingold, A. L., S. A. Cohn, and J. M. Scholey. 1988. J. Cell Biol. 107:2657-2667) detected antigens associated with both the ER and microtubules. On immunoblots they recognized microtubule associated polypeptide(s) of approximately 115 kD from Xenopus eggs. These observations are consistent with a role for kinesin in creating movement between the microtubules and ER, which leads in turn to the cortical rotation.

Organization and regulation of cortical microtubules during the first cell cycle of Xenopus eggs

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 699-709 ◽  
Author(s):  
M.M. Schroeder ◽  
D.L. Gard
Keyword(s):  
Cell Cycle ◽  
Cortical Microtubule ◽  
Cortical Microtubules ◽  
Confocal Immunofluorescence Microscopy ◽  
Confocal Immunofluorescence ◽  
Vegetal Cortex ◽  
M Phase ◽  
Tubulin Antibodies ◽  
Microtubule Networks ◽  
Sperm Aster

Anti-tubulin antibodies and confocal immunofluorescence microscopy were used to examine the organization and regulation of cytoplasmic and cortical microtubules during the first cell cycle of fertilized Xenopus eggs. Appearance of microtubules in the egg cortex temporally coincided with the outgrowth of the sperm aster. Microtubules of the sperm aster first reached the animal cortex at 0.25, (times normalized to first cleavage), forming a radially organized array of cortical microtubules. A disordered network of microtubules was apparent in the vegetal cortex as early as 0.35. Cortical microtubule networks of both animal and vegetal hemispheres were reorganized at times corresponding to the cortical rotation responsible for specification of the dorsal-ventral (D-V) axis. Optical sections suggest that the cortical microtubules are continuous with the microtubules of the sperm aster in fertilized eggs, or an extensive activation aster in activated eggs. Neither assembly and organization, nor disassembly of the cortical microtubules coincided with MPF activation during mitosis. However, cycloheximide or 6-dimethylaminopurine, which arrest fertilized eggs at interphase, blocked cortical microtubule disassembly. Injection of p13, a protein that specifically inhibits MPF activation, delayed or inhibited cortical microtubule breakdown. In contrast, eggs injected with cyc delta 90, a truncated cyclin that arrest eggs in M-phase, showed normal microtubule disassembly. Finally, injection of partially purified MPF into cycloheximide-arrested eggs induced cortical microtubule breakdown. These results suggest that, despite a lack of temporal coincidence, breakdown of the cortical microtubules is dependent on the activation of MPF.

scholarly journals The nanoscale organization of the Wnt signaling integrator Dishevelled in the development-essential vegetal cortex domain of an egg and early embryo

2021 ◽  
Author(s):  
John H. Henson ◽  
Bakary Samasa ◽  
Charles B. Shuster ◽  
Athula H. Wikramanayake
Keyword(s):  
Plasma Membrane ◽  
Sea Urchin ◽  
Super Resolution ◽  
Cell Types ◽  
Early Embryo ◽  
Ultrastructural Organization ◽  
C Terminus ◽  
Pathway Activation ◽  
Vegetal Cortex ◽  
Canonical Wnt

AbstractWnt/β-catenin (cWnt) signaling is a crucial regulator of development and Dishevelled (Dsh/Dvl) functions as an integral part of this pathway by linking Wnt binding to the frizzled:LRP5/6 receptor complex with β-catenin-stimulated gene expression. In many cell types Dsh has been localized to ill-defined cytoplasmic puncta, however in sea urchin eggs and embryos confocal fluorescence microscopy has shown that Dsh is localized to puncta present in a novel and development-essential vegetal cortex domain (VCD). In the present study, we used super-resolution light microscopy and platinum replica TEM to provide the first views of the ultrastructural organization of Dsh within the sea urchin VCD. 3D-SIM imaging of isolated egg cortices demonstrated the concentration gradient-like distribution of Dsh in the VCD, whereas higher resolution STED imaging revealed that some individual Dsh puncta consisted of more than one fluorescent source. Platinum replica immuno-TEM localization showed that Dsh puncta on the cytoplasmic face of the plasma membrane consisted of aggregates of pedestal-like structures each individually labeled with the C-terminus specific Dsh antibody. These aggregates were resistant to detergent extraction and treatment with drugs that disrupt actin filaments or inhibit myosin II contraction, and coexisted with the first division actomyosin contractile ring. These results confirm and extend previous studies and reveal, for the first time in any cell type, the nanoscale organization of plasma membrane tethered Dsh. Our current working hypothesis is that these Dsh pedestals represent a prepositioned scaffold organization that is important for canonical Wnt pathway activation at the sea urchin vegetal organization and may also be relevant to the submembranous Dsh puncta present in other eggs and embryos.

Microtubule organization during the cell cycle of the primitive eukaryote dinoflagellate Crypthecodinium cohnii

1993 ◽  
Vol 104 (3) ◽  
pp. 639-651 ◽  
Author(s):  
E. Perret ◽  
J. Davoust ◽  
M. Albert ◽  
L. Besseau ◽  
M.O. Soyer-Gobillard
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Laser Scanning ◽  
Confocal Laser ◽  
Cortical Microtubules ◽  
Microtubule Organization ◽  
Late Prophase ◽  
Crypthecodinium Cohnii ◽  
Pass Through ◽  
Microtubular System

The complete microtubular system of the dinoflagellate Crypthecodinium cohnii Biecheler is described, as seen by confocal laser scanning fluorescence microscopy and labelling with anti-beta-tubulin antibody. This technique allowed us to observe the organization of the subcortical and internal cytoskeletons and the mitotic microtubular system, and their changes during the cell cycle. These observations are compared with those made in cryosections by light microscopy and in fast-freeze-fixed, cryosubstituted cells by electron microscopy. We show the organization of the cortical microtubules, and in particular of the thick microtubular bundles arranged as a three-pronged fork from which they seem to emanate. This fork emerges from a peculiar cytoplasmic zone at the pole of the cell and is in contact with the region of the kinetosomes, at the cingulum. During the G1 phase, only a single, radial microtubular bundle (a “desmose”) is observable in the inner part of the cytoplasm. One of its ends is near the flagellar bases and the other end is close to the nucleus in the centrosome region. During the S phase, the flagella drop off, the cell encysts and the kinetosomes duplicate. In mitosis, the cortical microtubules and the intracytoplasmic microtubular bundles do not depolymerize. The microtubular fork, desmose and centrosome double and migrate, while the divided kinetosomes stay in the same place. Later, the centrosomes organize the extranuclear spindle, which is connected to the kinetosome region by the microtubular desmose. The convergent end of the three-pronged fork seems to be in contact with the centrosome region. In early and mid-prophase, thick microtubular bundles pass through the nucleus in cytoplasmic channels and converge towards the two poles. Asters were never seen at the spindle poles. The channels and microtubular bundles in the spindle double in number during late prophase and lengthen in early anaphase. The spindle bundles diverge in late anaphase, extend to very near the plasma membrane and depolymerize during telophase. The cleavage furrow in which tubulin and actin are characterized appears in anaphase, formed by invagination of plasma membrane in the kinetosome region. The structure and rearrangements of the Crypthecodinium cohnii microtubular system are compared with those of other dinoflagellates and protists and of higher eukaryotes.

scholarly journals Presence of a protein immunologically related to lamin B in the postsynaptic membrane of Torpedo marmorata electrocyte.

1989 ◽  
Vol 109 (4) ◽  
pp. 1745-1752 ◽  
Author(s):  
A Cartaud ◽  
J C Courvalin ◽  
M A Ludosky ◽  
J Cartaud
Keyword(s):  
Plasma Membrane ◽  
Polyclonal Antibodies ◽  
Postsynaptic Membrane ◽  
Relative Molecular Mass ◽  
Membrane Domains ◽  
Lamin B ◽  
Cell Biol ◽  
Membrane Contacts ◽  
Intermediate Size ◽  
Cytoplasmic Side

The Torpedo electrocyte is a flattened syncytium derived from skeletal muscle, characterized by two functionally distinct plasma membrane domains. The electrocyte is filled up with a transversal network of intermediate filaments (IF) of desmin which contact in an end-on fashion both sides of the cell. In this work, we show that polyclonal antibodies specific for lamin B recognizes a component of the plasma membrane of Torpedo electrocyte. This protein which thus shares epitopes with lamin B has a relative molecular mass of 54 kD, an acidic IP of 5.4. It is localized exclusively on the cytoplasmic side of the innervated membrane of the electrocyte at sites of IF-membrane contacts. Since our previous work showed that the noninnervated membrane contains ankyrin (Kordeli, E., J. Cartaud, H. O. Nghiêm, L. A. Pradel, C. Dubreuil, D. Paulin, and J.-P. Changeux. 1986. J. Cell Biol. 102:748-761), the present results suggest that desmin filaments may be anchored via the 54-kD protein to the innervated membrane and via ankyrin to the noninnervated membrane. These findings would represent an extension of the model proposed by Georgatos and Blobel (Georgatos, S. D., and G. Blobel. 1987a. J. Cell Biol. 105:105-115) in which type III intermediate size filaments are vectorially inserted to plasma and nuclear membranes by ankyrin and lamin B, respectively.

Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary

1970 ◽  
Vol 28 ◽  
pp. 328-329
Author(s):  
J. R. Ruby ◽  
R. F. Dyer ◽  
R. G. Skalko ◽  
R. F. Gasser ◽  
E. P. Volpe
Keyword(s):  
Germ Cells ◽  
Rana Pipiens ◽  
Comparative Morphology ◽  
Dense Material ◽  
Individual Species ◽  
Microscope Examination ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Cytoplasmic Side ◽  
Intercellular Connections

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.

The extracellular matrix of echinoderm and amphibian eggs: Visualization in quick-frozen, deep-etched, and rotary-shadowed specimens

1990 ◽  
Vol 48 (3) ◽  
pp. 60-61
Author(s):  
Barry Bonnell ◽  
Carolyn Larabell ◽  
Douglas Chandler
Keyword(s):  
Extracellular Matrix ◽  
Plasma Membrane ◽  
Sea Urchin ◽  
Crystalline Structure ◽  
Cortical Granule ◽  
Two Dimensional ◽  
Small Peptides ◽  
Deep Etching ◽  
Quick Freezing ◽  
Acrosomal Reaction

Eggs of many species including those of echinoderms, amphibians and mammals exhibit an extensive extracellular matrix (ECM) that is important both in the reception of sperm and in providing a block to polyspermy after fertilization.In sea urchin eggs there are two distinctive coats, the vitelline layer which contains glycoprotein sperm receptors and the jelly layer that contains fucose sulfate glycoconjugates which trigger the acrosomal reaction and small peptides which act as chemoattractants for sperm. The vitelline layer (VL), as visualized by quick-freezing, deep-etching, and rotary-shadowing (QFDE-RS), is a fishnet-like structure, anchored to the plasma membrane by short posts. Orbiting above the VL are horizontal filaments which are thought to anchor the thicker jelly layer to the egg. Upon fertilization, the VL elevates and is transformed by cortical granule secretions into the fertilization envelope (FE). The rounded casts of microvilli in the VL are transformed into angular peaks and the envelope becomes coated inside and out with sheets of paracrystalline protein having a quasi-two dimensional crystalline structure.

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