Calcium influx is required for phosphatidylserine exposure during mouse egg activation

GÓMEZ ELÍAS MD; CUASNICÚ PS; COHEN DJ

Chascomús

Jornada; XVI Jornadas de la Sociedad Argentina de Biología; 2014

Sociedad Argentina de Biología (SAB)

Intracellular Ca2+ increase after fertilization is essential to initiate egg activation. We have recently found that this Ca2+ rise results in a transient exposure of phosphatidylserine (PS) in fertilized eggs that is not associated with apoptosis. The aim of this work was to evaluate the source of Ca2+ involved in PS exposure in activated eggs. The incubation of eggs with different known parthenogenetic egg activators showed that whereas SrCl2 and ethanol induced PS exposure, Ca2+ ionophore A23187 did not. Given that, differently from SrCl2 and ethanol, the Ca2+ increase produced by A23187 is originated from intracellular sources, we next evaluated whether extracellular Ca2+ influx was necessary to induce the translocation of PS. For this purpose, eggs were incubated with either 2-APB, a membrane Ca2+ channel agonist, or thimerosal that induces Ca2+ oscillations by releasing this ion from the endoplasmic reticulum, and the presence of externalized PS was evaluated. In parallel, two parameters of egg activation (i.e. cortical granule exocytosis and resumption of meiosis) were also evaluated. Whereas 2-APB and thimerosal produced high percentages of egg activation, only 2-APB was able to induce PS exposure. Altogether, these results indicate that Ca2+ influx from extracellular medium is required for the mobilization of PS during egg activation.