Degradation of the unlaid Xenopus eggs. In the ovaries, fully grown apoptosis-resistant oocytes are naturally arrested in prophase I with the low activity of CSF and MPF. After hormone-induced ovulation, a number of matured eggs now arrested at the metaphase II by the high activity of CSF and MPF are retained in the frog genital tract. They experience spontaneous meiotic exit and initiate a classical cytochrome c-mediated apoptotic program, accompanied by global proteolysis of intracellular proteins. Finally, the eggs completely deteriorate and lose their integrity inside the frog body.
Iguchi et al. BMC Cell Biology 2013 14:11 doi:10.1186/1471-2121-14-11