title: Mineral-bearing vesicle transport in sea urchin embryos.
abstract: Sea urchin embryos sequester calcium from the sea water. This calcium is deposited in a concentrated form in granule bearing vesicles both in the epithelium and in mesenchymal cells. Here we use in vivo calcein labeling and confocal Raman spectroscopy, as well as cryo-FIB-SEM 3D structural reconstructions, to investigate the processes occurring in the internal cavity of the embryo, the blastocoel. We demonstrate that calcein stained granules are also present in the filopodial network within the blastocoel. Simultaneous fluorescence imaging and Raman spectroscopy show that these granules do contain a calcium mineral. By tracking the movements of these granules, we show that the granules in the epithelium and primary mesenchymal cells barely move, but those in the filopodial network move long distances. We could however not detect any unidirectional movement of the filopodial granules. We also show the presence of mineral containing multivesicular vesicles that also move in the filopodial network. We conclude that the filopodial network is an integral part of the mineral transport process, and possibly also for sequestering calcium and other ions. Although much of the sequestered calcium is deposited in the mineralized skeleton, a significant amount is used for other purposes, and this may be temporarily stored in these membrane-delineated intracellular deposits.
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Netta
authors.initials: N
authors.lastname: Vidavsky
authors.affiliation: Max-Planck Institute of Colloids and Interfaces, Department of Biomaterials, Potsdam, Germany.
authors.forename: Admir
authors.initials: A
authors.lastname: Masic
authors.affiliation: Carl Zeiss Microscopy GmbH, Global Applications Support, Carl-Zeiss-Straße 22, D-73447 Oberkochen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schertel
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Steve
authors.initials: S
authors.lastname: Weiner
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel. Electronic address: Lia.Addadi@weizmann.ac.il.
authors.forename: Lia
authors.initials: L
authors.lastname: Addadi
mesh_terms: D000818:Animals; D001692:Biological Transport; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism*; D002119:Calcium Carbonate / Q000378:metabolism; D020285:Cryoelectron Microscopy; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D047328:Paracentrotus / Q000196:embryology*; D011554:Pseudopodia / Q000378:metabolism*; D013059:Spectrum Analysis, Raman
chemical_list: D002119:Calcium Carbonate; D002118:Calcium
keywords: Biomineralization; Cryo-FIB-SEM; Filopodia; Raman spectroscopy; Sea urchin spicule; Vesicle transport