Antiapoptotic role for ornithine decarboxylase during oocyte maturation.

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is a nonredundant and essential gene in all eukaryotes. During the mitotic cell cycle, ODC exhibits two activity peaks: one at the G(1)/S transition and one during the G(2)/M transition. The physiological role of this cell cycle-dependent ODC activity dynamic is not clear.

Polar body emission requires a RhoA contractile ring and Cdc42-mediated membrane protrusion.

Vertebrate oocyte maturation is an extreme form of asymmetric cell division, producing a mature egg alongside a diminutive polar body. Critical to this process is the attachment of one spindle pole to the oocyte cortex prior to anaphase. We report here that asymmetric spindle pole attachment and anaphase initiation are required for localized cortical activation of Cdc42, which in turn defines the surface of the impending polar body.