Figure 4

Inhibition of Cdk2 triggers apoptosis. One-cell stage embryos were injected with 5 ng of Δ34-Xic1 or p27Xic1CK- (control) protein. (A) Embryos expressing Δ34-Xic1 were delayed approximately one cell cycle at Stage 8 (5 hr pf) compared to p27Xic1CK- controls. At Stage 11 (12 hr pf), embryos expressing Δ34-Xic1 exhibited abnormal morphology consistent with apoptosis compared to p27Xic1CK- controls, which gastrulated. p27Xic1CK- controls continued to develop through gastrulation and formed a neural groove, evident at Stage 13 (16 hr pf). (B) Extracts of Stage 11 embryos were incubated with recombinant PARP, a substrate for caspase 3 [4]. The presence of a cleaved PARP fragment indicates caspase activity. Replicate samples are shown.