Developmental regulation of induced and programmed cell death in Xenopus embryos

We have analyzed the role of cell death during early Xenopus development and have identified two distinct types of cell death programs during the period between fertilization and the tadpole stage. One is a maternal cell death program that is activated at the onset of gastrulation following damage to the pre-midblastula transition embryo, resulting in the death of non-viable cells. The activation of this cell death program at a specific time during development is a maternally programmed event under the control of a developmental timer set at fertilization, and does not depend on the type of stress applied, on cell cycle progression, or de novo protein synthesis. Subsequently, a second program corresponding to programmed cell death is initiated as part of the normal development of the embryo. Programmed cell death starts at the onset of gastrulation and we have analyzed its spatio-temporal patterns by a whole-mount in situ DNA end labeling technique (the TUNEL protocol).