IBYME   02675
INSTITUTO DE BIOLOGIA Y MEDICINA EXPERIMENTAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Fertilization induces a transient exposure of phosphatidylserine in mouse eggs
Autor/es:
CURIA A; ERNESTO JI; CUASNICU PS; COHEN D.J
Lugar:
New Hampshire, Estados Unidos
Reunión:
Congreso; Gordon Research Conference; 2011
Institución organizadora:
Gordon Research Conference.
Resumen:
Phosphatidylserine (PS) is a phospholipid localized in the inner leaflet of the plasma membrane, and its exposure is a marker for apoptosis. Recent evidence suggests that this exposure could also be associated with several non-apoptotic events including viral fusion and sperm capacitation. In view of this, we evaluated the role of PS exposure during gamete fusion. However, the blockage of PS during mouse gamete co-incubation by the addition of FITC-conjugated Anexin 5 (ANX5), a protein that specifically binds to PS, had no effect on the percentage of fertilized eggs at any of the concentration tested. Unexpectedly, fertilized eggs presented a positive labelling for ANX5 on their surface that was observed both in intact and zona-free fertilized eggs, and not detected in non-inseminated or non-fertilized eggs. Ca2+-ionophore activated eggs did not present fluorescent labelling suggesting that the observed PS exposure was not due to a membrane disorder produced by the cortical granules exocytosis. By contrast, eggs activated with SrCl2 or ethanol presented a labelling similar to that observed in fertilized eggs, evidencing the existence of differences between parthenogenetic activation methods. The follow-up and quantification of the labelling on fertilized eggs showed that at the sperm-head-decondensed stage, the fluorescence was observed on the entire egg surface with the exception of the regions corresponding to the membrane overlying the meiotic spindle and the sperm entry site. At the two pronucleous stage, the egg surface area exposing PS was smaller but the fluorescence intensity within these areas was similar to that observed in the previous stage. ANX5-labelling was undetectable in two-cell embryos. Finally, RT-PCR analysis showed the expression in eggs of two scramblases (PLSCR1 and PLSCR3) and two flipasses (ATP8A1 y ATP8A2) suggesting that these enzymes could regulate the kinetics of PS exposure in fertilized eggs. Altogether, results show for the first time the existence of a transient exposure of PS in fertilized eggs not associated with apoptosis that could play a role during egg activation.