Apoptosis in sea urchin oocytes, eggs, and early embryos

Certain experimental manipulations with sea urchin oocytes, eggs, and early embryos result in induction of cell death. We were interested in whether or not these cells possessed functional apoptotic machinery, and whether cellular demise under certain experimental conditions is due to activation of a programmed cell death pathway. Therefore, we evaluated a number of apoptosis assays in sea urchin oocytes, eggs, and early embryos experimentally induced to apoptose with staurosporine. Our results indicate that these cells each possess and activate necessary apoptotic machinery that leads to characteristic apoptotic phenotypes. The eggs of this animal have completed meiosis, and are quiescent transcriptionally, translationally, and metabolically. Surprisingly, they still undergo apoptosis. The progression through apoptosis of treated specimens could be followed by morphological changes of the cells, by chromatin condensation and degradation, and by activation of caspases. The similarities and differences in the execution of apoptosis between the cell types studied are discussed. Results of this study will be useful for interpreting experiments in these model systems in which different molecules are targeted for interference and which brings about cell death.