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Storage, ultrastructural targeting and function of toposomes and hyalin in sea urchin embryogenesis.
Journal article

Storage, ultrastructural targeting and function of toposomes and hyalin in sea urchin embryogenesis.

  • 1991-02-01
Published in:
  • Mechanisms of development. - 1991
Animals
Blastocyst
Cold Temperature
Cryopreservation
Egg Proteins
Glycoproteins
Hyalin
Immunoblotting
Immunohistochemistry
Microscopy, Electron
Sea Urchins
English This study compares by immunogold labeling the ultrastructural localization of a hexameric 22S glycoprotein, called toposome, with that of hyalin in unfertilized eggs and cells of hatched sea urchin blastulae. Nearly all hyalin is present in the electron translucent compartment of the cortical granules and in the translucent non-cortical pigment granules. In the blastula both of these intracellular stores have vanished and hyalin now forms a broad band below the apical lamina. By contrast, in the egg toposomes are present on the surface, as well as stored in yolk granules and in the electron dense lamellar compartment of the cortical granules. In the hatched blastula, toposomes that have been modified by limited proteolysis in the yolk granules, are associated with the plasma membranes of all newly formed cells, while the toposomes originating from the cortical granules have been incorporated as unmodified 160 kDa polypeptides into an extracellular double layer enveloping the embryo on the outside of the hyaline layer. From evidence discussed in detail, we conclude that the extracellular toposomes rivet the apical lamina to the surface and underlying cytoskeleton of the microvilli, while the modified toposomes from the yolk granules are responsible for position specific intercellular adhesion as they are released to the surface of newly formed cells. We propose that all the material stored in yolk granules is utilized for the assembly of new membranes.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/43896
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