2 research outputs found
A functional genomic and proteomic perspective of sea urchin calcium signaling and egg activation.
The sea urchin egg has a rich history of contributions to our understanding of fundamental questions of egg activation at fertilization. Within seconds of sperm-egg interaction, calcium is released from the egg endoplasmic reticulum, launching the zygote into the mitotic cell cycle and the developmental program. The sequence of the Strongylocentrotus purpuratus genome offers unique opportunities to apply functional genomic and proteomic approaches to investigate the repertoire and regulation of Ca(2+) signaling and homeostasis modules present in the egg and zygote. The sea urchin "calcium toolkit" as predicted by the genome is described. Emphasis is on the Ca(2+) signaling modules operating during egg activation, but the Ca(2+) signaling repertoire has ramifications for later developmental events and adult physiology as well. Presented here are the mechanisms that control the initial release of Ca(2+) at fertilization and additional signaling components predicted by the genome and found to be expressed and operating in eggs at fertilization. The initial release of Ca(2+) serves to coordinate egg activation, which is largely a phenomenon of post-translational modifications, especially dynamic protein phosphorylation. Functional proteomics can now be used to identify the phosphoproteome in general and specific kinase targets in particular. This approach is described along with findings to date. Key outstanding questions regarding the activation of the developmental program are framed in the context of what has been learned from the genome and how this knowledge can be applied to functional studies.</p
Oxygen Spectroscopy and Polarization-Dependent Imaging Contrast (PIC)-Mapping of Calcium Carbonate Minerals and Biominerals
X-ray
absorption near-edge structure (XANES) spectroscopy and spectromicroscopy
have been extensively used to characterize biominerals. Using either
Ca or C spectra, unique information has been obtained regarding amorphous
biominerals and nanocrystal orientations. Building on these results,
we demonstrate that recording XANES spectra of calcium carbonate at
the oxygen K-edge enables polarization-dependent imaging contrast
(PIC) mapping with unprecedented contrast, signal-to-noise ratio,
and magnification. O and Ca spectra are presented for six calcium
carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite,
and both hydrated and anhydrous amorphous calcium carbonate. The crystalline
minerals reveal excellent agreement of the extent and direction of
polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong
for aragonite, calcite, and vaterite. In natural biominerals, oxygen
PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic
structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite
crystals at the nacre–prismatic boundary and the narrowest
calcite needle-prisms. In the tunic spicules of Herdmania
momus, O PIC-mapping revealed the size and arrangement
of some of the largest vaterite single crystals known. O spectroscopy
therefore enables the simultaneous measurement of chemical and orientational
information in CaCO<sub>3</sub> biominerals and is thus a powerful
means for analyzing these and other complex materials. As described
here, PIC-mapping and spectroscopy at the O K-edge are methods for
gathering valuable data that can be carried out using spectromicroscopy
beamlines at most synchrotrons without the expense of additional equipment