Unfertilized Xenopus Eggs Die by Bad-Dependent Apoptosis under the Control of Cdk1 and JNK
Figure 4
ERK1 is inactivated in response to apoptosis whereas Cdk1 inactivation occurs during egg aging, independently of apoptosis.
Fully-grown prophase oocytes were isolated from the ovaries, stimulated by 1 µM progesterone (+Pg, time 0) or not (−Pg) and then incubated for various times. Three females were used, one in (A), another in (B) and (C) and one in (D). (A) Western blot analysis of cytosolic fractions of unfertilized eggs was performed at various times after progesterone stimulation with antibodies against ERK1, the active phosphorylated form of ERK1 (p-ERK1), Mos, Cyt c and active caspase 3 (casp-3). The percentage of eggs undergoing apoptosis after morphological analysis is indicated at the bottom, the incubation times in hours (Hrs) are indicated at the top. (B) H1 kinase activity of Cdk1 and apoptotic death were assayed in eggs at various times (in Hours, Hrs) after progesterone stimulation. (C) Western blot analysis of cytosolic fractions of unfertilized eggs was performed at various times after progesterone stimulation (+Pg) with antibodies against ERK1, cyclin B2 (Cyc B2) and the Ser10-phosphorylated form of histone H3 (p-H3). The incubation times in hours (Hrs) are indicated at the top. (D) Oocytes were microinjected with either GFP or GFP-XR11 mRNA and then stimulated by progesterone (time 0). Western blot analysis of cytosolic fractions of unfertilized eggs was performed at various times after progesterone stimulation with antibodies against ERK1, the active phosphorylated form of ERK1 (p-ERK1), cyclin B2 (Cyc B2) and Cyt c. The incubation times in hours (Hrs) are indicated at the top.