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Cellular control over spicule formation in sea urchin embryos: A structural approach
E Beniash1, L Addadi, S Weiner
1Department of Structural Biology, Weizmann Institute of Science, Rehovot, 76100, Israel.
Journal of Structural Biology
|April 10, 1999
Summary
Sea urchin embryo spicules form within membrane-bound compartments. Amorphous calcium carbonate transforms into calcite, with the surrounding membrane controlling mineralization and material exchange.
Area of Science:
- Developmental Biology
- Biomineralization
- Cell Biology
Background:
- Sea urchin spicules are crucial skeletal elements.
- Spicule formation involves precise control over mineral deposition.
- The cellular mechanisms underlying spiculogenesis are not fully understood.
Purpose of the Study:
- To investigate the relationship between the membrane of the spiculogenic compartment and the mineral phase during sea urchin spicule formation.
- To elucidate the role of intracellular compartments and precursor materials in spicule biomineralization.
Main Methods:
- Transmission electron microscopy (TEM) utilizing freeze-fracture techniques.
- Analysis of spicule-forming compartments and associated membranes.
- Electron diffraction to identify mineral composition within cellular granules.
Main Results:
- Spicules form within membrane-delineated compartments, tightly enclosed by the membrane.
- Electron-dense granules within spiculogenic cells contain amorphous calcium carbonate, identified as the precursor mineral phase.
- Membrane-associated structures suggest active material transport and control over mineralization.
Conclusions:
- The membrane surrounding the spiculogenic compartment plays a vital role in regulating material transport and controlling calcite mineralization during spicule formation.
- Amorphous calcium carbonate granules serve as the direct source of mineral for spicule growth.
- Intracellular compartments are essential for controlled biomineralization in sea urchin embryos.