Centromere localization changes in oocyte nuclei during mouse folliculogenesis

During folliculogenesis, the oocyte undergoes changes in chromatin organization that are functional to the acquisition of the developmental competence. In the antral compartment of the mouse ovary, two types of oocytes have been described on the basis of the presence or absence of a ring of Hoechst-bright fluorescence around the nucleolus. It is not known whether these changes of chromatin organization entail changes in the localization of chromosomal domains. Making use of CREST serum against centromeric proteins and confocal microscopy, here we describe the three-dimensional localization of the centromeres within the nuclear volume of mouse antral oocytes. Our data reveal that centromeres change localization during oocyte maturation showing a dramatic coalescence around the nucleolus surface at the stages preceding ovulation. These results further our knowledge on the nuclear organization of the mouse oocyte and represent a first and necessary contribution for future studies on the role that nuclear architecture may exert as an epigenetic regulator of genome functioning.