Cortical granule translocation during maturation of starfish oocytes requires cytoskeletal rearrangement triggered by InsP3-mediated Ca2+ release.

Cortical granules (secretory vesicles located under the cortex of mature oocytes) release their contents to the medium at fertilization. Their exocytosis modifies the extracellular environment, blocking the penetration of additional sperm. The granules translocate to the surface during the maturation process, and it has been suggested that they move to the cortex via cytoskeletal elements. In this paper we show that the increase in intracellular Ca2+, which the maturing hormone 1-methyladenine (1-MA) induces in starfish through the activation of inositol 1,4, 5-trisphosphate (InsP3) receptors, triggers changes in filamentous actin, which then direct the correct movement and reorientation of the cortical granules and the elevation of the fertilization envelope.