Live imaging of cortical granule exocytosis reveals that in vitro matured mouse oocytes are not fully competent to secret their content

CAPPA AI; DE PAOLA MM; WETTEN, P; DE BLAS G; MICHAUT MA

Biology Open

Steven Kelly

Año: 2018

2046-6390

Oocyte in vitro maturation does not entirely support all the nuclear and cytoplasmic changesthat occur physiologically and it is poorly understood whether in vitro maturation affects thecompetence of cortical granules to secret their content during cortical reaction. Here, wecharacterize cortical granule exocytosis (CGE) in live mouse oocytes activated by strontiumchloride using the fluorescent lectin FITC-LCA. We compared the kinetic of CGE betweenovulated (in vivo matured, IVO) and in vitro matured (IVM) mouse oocytes. Results showthat: 1) IVM oocytes have a severely reduced response to strontium chloride; 2) the lowresponse was confirmed by quantification of remnant cortical granules in permeabilized cellsand by a novel method to quantify the exudate in non permeabilized cells; 3) the kinetic ofCGE in IVO oocytes was rapid and synchronous; 4) the kinetic of CGE in IVM oocytes wasdelayed and asynchronous; 5) cortical granules in IVM oocytes show an irregular limit withthe cortical granule free domain. We propose the analysis of CGE in live oocytes as abiological test to evaluate the competence of IVM mouse oocytes.