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Updated: Aug 8, 2026
Analysis of Apoptosis in Zebrafish Embryos by Whole-mount Immunofluorescence to Detect Activated Caspase 3
Published on: December 20, 2013
Analysis of caspase-3, caspase-8 and caspase-9 enzymatic activities in mouse oocytes and zygotes
Adrian Papandile1, David Tyas, Donald M O'Malley
1Biology Department, Northeastern University, Boston, Massachusetts 02115, USA.
Abstract:
The current consensus in the literature is that ovulated oocytes that are not fertilized die by apoptosis, but the details of the proteins involved in the apoptotic pathways have not been elucidated. In this paper we confirm that caspase-3, the executioner of apoptosis, is expressed in mouse oocytes, and show that two initiators of apoptosis, caspase-8 and caspase-9, are expressed in mouse oocytes. Comparisons were made of caspase-3, -8, and -9 activities in superovulated oocytes that were freshly collected or allowed to age in vivo or in vitro. We found that caspase-3 activity significantly increased in aged oocytes compared with young oocytes (p < 0.001), and that both caspase-8 activity and caspase-9 activity decreased in aged oocytes compared with young oocytes (p < 0.001 for caspase-8 and p < 0.05 for caspase-9 activity). A comparison of superovulated with naturally ovulated oocytes showed the same amount of caspase-8 activity in each, but a significant (p < 0.001) decrease in caspase-9 activity in naturally ovulated compared with superovulated oocytes. There was no difference in caspase-3, -8, or -9 activity in oocytes compared with zygotes. Finally, we showed that culture of oocytes in staurosporine increased the activity of caspase-8 and caspase-9. In conclusion, the finding of both caspase-8 and caspase-9 activity in oocytes shows that unfertilized oocytes have the machinery to undergo apoptosis by using either the extrinsic (caspase-8 dependent) or intrinsic (caspase-9 dependent) pathways.
Insights
Unfertilized mouse oocytes can undergo apoptosis through caspase-8 or caspase-9 pathways. Caspase-3 activity increases with oocyte aging, while caspase-8 and caspase-9 activities decrease.
Area of Science:
- Reproductive Biology
- Cellular Biology
- Apoptosis Research
Background:
- Unfertilized oocytes are thought to undergo apoptosis, but the specific proteins involved remain unclear.
- Apoptosis, or programmed cell death, is a critical process in cellular regulation.
Purpose of the Study:
- To investigate the expression and activity of key apoptosis-related caspases (caspase-3, -8, and -9) in mouse oocytes.
- To determine how oocyte aging and ovulation methods affect caspase activity.
Main Methods:
- Analysis of caspase-3, -8, and -9 expression and activity in freshly collected, aged (in vivo and in vitro), and naturally ovulated mouse oocytes.
- Comparison of caspase activity between oocytes and zygotes.
- Assessment of caspase activity following staurosporine-induced apoptosis in vitro.
Main Results:
- Caspase-3 activity significantly increased in aged oocytes.
- Caspase-8 and caspase-9 activities decreased in aged oocytes.
- Naturally ovulated oocytes showed lower caspase-9 activity compared to superovulated oocytes, with no difference in caspase-8.
Conclusions:
- Mouse oocytes express both caspase-8 and caspase-9, indicating the capacity for apoptosis via extrinsic and intrinsic pathways.
- Oocyte aging and ovulation method influence caspase activity, suggesting complex regulatory mechanisms.
- No significant difference in caspase activity was observed between oocytes and zygotes.
