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

Speksnijder, Johanna E.; Jong, Kees de; Wisselaar, H. A.; Linnemans, W. A. M.; Dohmen, Marc

doi:10.1007/bf02438936

Cited by 8 publications

(6 citation statements)

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“…Our previous study on the ultrastructural organization of the Nassarius egg cortex has demonstrated the presence of a network o f actin filaments (Speksnijder et al 1989). Conventional fluores;zence microscopy o f whole eggs stained with NBD-phallacidin, which is k n o w n to specifically label F-actin (Barak et al 1980), confirms this earlier study (Fig.…”

Section: Effects Of Con a On The Cortical Actin Networksupporting

confidence: 65%

“…In addition, washing off the bound Con A with eMG before polar lobe formation completely prevents the occurrence of Con A effects, whereas removal of bound Con A is no longer effective in completely preventing the effects of Con A once the eggs start forming a polar lobe. The increased ability of Con A binding sites to cross-link at the time of polar lobe formation coincides with an increased lateral mobility of plasma membrane lipids in the vegetal membrane (Speksnijder et al 1985a), as well as with a disappearance of microtubules from the egg cortex (Speksnijder et al 1989). These findings suggest that, before lobe formation (i.e.…”

Section: Discussionmentioning

confidence: 94%

“…It is possible that cross-linking of Con Abinding sites activates the polyphosphoinositide signal transduction pathway (Berridge and Irvine 1989), resulting in the production of 1,4,5-inositol trisphosphate (InsP3), which in turn releases calcium from intracellular stores such as the endoplasmic reticnlum (ER). It is important to note that the Nassarius egg is known to contain an elaborate network of endoplasmic reticulum (Speksnijder et al 1989) comparable to that found in other invertebrate marine eggs in which the ER is considered as the most important calcium regulating organelle (e.g. Gualtieri and Sardet 1989).…”

Section: Discussionmentioning

confidence: 99%

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Polar effects of concanavalin A on the cortical cytoskeleton of a molluscan egg (Nassarius reticulatus, Gastropoda)

Speksnijder

Teerds

Hage

et al. 1991

Roux's Arch Dev Biol

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The organization of the surface of fertilizedNassarius reticulatus eggs was probed by investigating the effects of treatment with concanavalin A (Con A). This lectin causes abnormal polar lobe formation as well as inhibition of cleavage. At low concentrations of Con A (0.3-1.0 μg/ml) the polar lobe constriction becomes considerably elongated, whereas at higher concentrations (2.5-50 μ/ml) the position of the constriction undergoes an extreme shift towards the animal pole. In the latter case, the surface of the animal part of the egg forms large protrusions and folds. Con A also causes resorption of microvilli and disappearance of the extracellular layer covering these villi; this process starts at the vegetal pole and propagates towards the animal pole. These changes in surface architecture are associated with profound changes in the organization of filamentous (F-) actin as assessed by confocal laser scanning microscopy of NBD-phallacidin-labelled eggs. Divalent succinyl-Con A has the same effects on polar lobe formation and surface architecture as tetravalent Con A, but only at very high concentrations (100-200 μg/ml), indicating that Con A exerts its effects by cross-linkage of its binding sites. Experiments with cytoskeleton inhibitors (cytochalasin D, colchicine, and nocodazole) reveal that in Con A-treated eggs - as in untreated eggs - microfilaments, but not microtubules, are involved in the formation of the polar lobe constriction. The calcium ion channel blocker D600 affects neither normal nor Con A-induced abnormal polar lobe formation, which suggests that influx of external calcium is not required. In contrast, treatment with TMB-8, an antagonist of internal calcium release, prevents the formation of a polar lobe in both normal and Con A-treated eggs. Finally, eggs from which the polar lobe has been removed prior to Con A treatment show none of the effects described, whereas isolated polar lobes react similarly to intact eggs. These results suggest that binding of Con A to sites present at the vegetal pole of the egg is responsible for the observed effects of the lectin.

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Section: Effects Of Con a On The Cortical Actin Networksupporting

confidence: 65%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

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Polar effects of concanavalin A on the cortical cytoskeleton of a molluscan egg (Nassarius reticulatus, Gastropoda)

Speksnijder

Teerds

Hage

et al. 1991

Roux's Arch Dev Biol

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“…Most work has concentrated on ER in the peripheral layer of the egg, the cortex. The cortical ER forms a two-dimensional network parallel to the plasma membrane with connections to the internal ER network (Campanella and Andreucetti, 1977;Sardet, 1984;Luttmer and Longo, 1985;Sardet and Chang, 1987;Henson et al, 1989;Speksnijder et al, 1989a;Houliston and Elinson, 1991). In sea urchin and ascidian eggs, this cortical ER is capable of calcium uptake and release and contains a high-capacity, low-affinity calciumbinding protein as well as a high concentration of calcium (Oberdorf et al, 1986;Payan et al, 1986;Oberdorf et al,animal hemisphere, and to the decreased velocity of the calcium wave at fertilization in the vegetal hemisphere (Kline and Nuccitelli, 1985;Busa and Nuccitelli, 1985).…”

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confidence: 99%

Polarity and reorganization of the endoplasmic reticulum during fertilization and ooplasmic segregation in the ascidian egg.

Speksnijder

Terasaki

Hage

et al. 1993

The Journal of Cell Biology

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Abstract. During the first cell cycle of the ascidian egg, two phases of ooplasmic segregation create distinct cytoplasmic domains that are crucial for later development. We recently defined a domain enriched in ER in the vegetal region of Phaltusia mammillata eggs. To explore the possible physiological and developmental function of this ER domain, we here investigate its organization and fate by labeling the ER network in vivo with DiICl6(3), and observing its distribution before and after fertilization in the living egg. In unfertilized eggs, the ER-rich vegetal cortex is overlaid by the ER-poor but mitochondria-rich subcortical myoplasm. Fertilization results in striking rearrangements of the ER network. First, ER accumulates at the vegetal-contraction pole as a thick layer between the plasma membrane and the myoplasm. This accompanies the relocation of the myoplasm toward that region during the first phase of ooplasmic segregation. In other parts of the cytoplasm, ER becomes progressively redistributed into ER-rich and ER-poor microdomains. As the sperm aster grows, ER accumulates in its centrosomal area and along its astral rays. During the second phase of ooplasmic segregation, which takes place once meiosis is completed, the concentrated ER domain at the vegetal-contraction pole moves with the sperm aster and the bulk of the myoplasm toward the future posterior side of the embryo. These results show that after fertilization, ER first accumulates in the vegetal area from which repetitive calcium waves are known to originate (Speksnijder, J. E. 1992. . This ER domain subsequently colocalizes with the myoplasm to the presumptive primary muscle cell region.T nE ER is a key cellular organelle involved in the synthesis of membrane lipids and proteins, secretion, and calcium homeostasis. Morphologically, it is organized as a continuous and extensive network of tubules and cisternae with typical three-way junctions. A number of recent studies have revealed that it is a highly dynamic structure which interacts with a variety of cellular constituents, including microtubules and actin filaments (Terasaki et al.,

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“…In Nassarius, however, a detailed study of isolated cortices (Fig. 18) has not revealed any dramatic differences in the organization of the cortical cytoskeleton between the vegetal pole and other areas (Speksnijder et al, 1989).…”

Section: Morphogenetic Plasmsmentioning

confidence: 99%

Cell lineage in molluscan development

Dohmen

1992

Microscopy Res & Technique

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Cell lineage specification in molluscs is brought about by two mechanism: the segregation of morphogenetic plasms and inductive cell interactions. The evidence for the existence of morphogenetic plasms is largely circumstantial, but in one species, Bithynia, such a plasm has been identified in the polar lobe that forms at first cleavage. Inductive cell interactions are thought to be a prerequisite for the development of a large number of tissues and organs. The most extensively studied example is the specification of the mesodermal stem cell in Lymnaea and Patella, which occurs between 5th and 6th cleavage through an interaction between one macromere and a large number of micromeres. Both segregation and induction are tuned to the animal-vegetal polarity of the egg, at least during early development. This polarity probably arises during oogenesis and is manifest in regional differentiations of the surface architecture of the egg, in the distribution of inner membrane particles in the plasma membrane, in membrane fluidity characteristics, in ionic conductance properties of the plasma membrane, etc. All these phenomena have in common that they represent properties of the egg surface, suggesting that the polarity of the egg is somehow imprinted into the plasma membrane and the cortex of the egg during oogenesis.

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

Cited by 8 publications

References 54 publications

Polar effects of concanavalin A on the cortical cytoskeleton of a molluscan egg (Nassarius reticulatus, Gastropoda)

Polar effects of concanavalin A on the cortical cytoskeleton of a molluscan egg (Nassarius reticulatus, Gastropoda)

Polarity and reorganization of the endoplasmic reticulum during fertilization and ooplasmic segregation in the ascidian egg.

Cell lineage in molluscan development

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