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Contributions of suboolemmal acidic vesicles and microvilli to the intracellular Ca2+ increase in the sea urchin eggs at fertilization
Vasilev, F.; Limatola, N.; Chun, J.T.; Santella, L. (2019). Contributions of suboolemmal acidic vesicles and microvilli to the intracellular Ca2+ increase in the sea urchin eggs at fertilization. International Journal of Biological Sciences 15(4): 757-775. https://dx.doi.org/10.7150/ijbs.28461
In: International Journal of Biological Sciences: Lake Haven. e-ISSN 1449-2288, more
Peer reviewed article  
Available in  Authors 
Keywords
    ASSEMBLEPlus Transnational Access
    Scientific Publication
    Marine/Coastal
Author keywords
    cortical flash, cortical granules, microvilli, fertilization, calcium, actin
Authors  Top 
  • Vasilev, F.
  • Limatola, N.
  • Chun, J.T.
  • Santella, L.
Abstract
    The onset of fertilization in echinoderms is characterized by instantaneous increase of Ca2+ in the egg cortex, which is called 'cortical flash', and the subsequent Ca2+ wave. While the cortical flash is due to the ion influx through L-type Ca2+ channels in starfish eggs, its amplitude was shown to be affected by the integrity of the egg cortex. Here, we investigated the contribution of cortical granules (CG) and yolk granules (YG) to the sperm-induced Ca2+ signals in sea urchin eggs. To this end, prior to fertilization, Paracentrotus lividus eggs were treated with agents that disrupt or relocate CG beneath the plasma membrane: namely, glycyl-L-phenylalanine 2-naphthylamide (GPN), procaine, urethane, and NH4Cl. All these pretreatments consistently suppressed the cortical flash in the fertilized eggs, and accelerated the decay kinetics of the subsiding Ca2+ wave in most cases. By contrast, centrifugation of the eggs, which stratifies organelles but not the CG, did not exhibit such changes except that the CF was much enhanced in the centrifugal pole where YG are localized. Surprisingly, we noted that pretreatment of the eggs with these CG-disrupting agents or with the inhibitors of L-type Ca2+ channels all drastically reduced the density of the microvilli and their individual shapes on the egg surface. Taken together, our results suggest that the integrity of the egg cortex ensures successful generation of the Ca2+ responses at fertilization, and that modulation of microvilli shape and density may serve as a mechanism of controlling ion flux across the plasma membrane.
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