Caspase-2(L), caspase-9, and caspase-3 during in vitro maturation and fragmentation of the mouse oocyte

Area of Science:

• Cell Biology
• Reproductive Biology
• Apoptosis Research

Background:

• Apoptotic pathways are known to control oocyte fragmentation.
• The specific role of caspases in oocyte maturation and apoptosis remains underexplored.
• Few studies investigate caspase involvement from prophase I to later meiotic stages.

Purpose of the Study:

• To investigate the presence and role of caspases in unfertilized ovulated oocytes during maturation.
• To determine if caspases are involved in doxorubicin-induced oocyte apoptosis.
• To elucidate the function of caspases in regulating the meiotic process.

Main Methods:

• Detection of caspase-2(L), caspase-9, and caspase-3 in zymogen and cleaved forms using Western blot.
• Immunofluorescence microscopy to visualize caspase localization in relation to chromatin and meiotic spindle.
• Inhibition of caspase activity using Z-VAD-fmk to assess effects on meiotic progression and apoptosis.

Main Results:

• Caspase-2(L), caspase-9, and caspase-3 were detected in oocytes prior to meiosis resumption.
• Caspase-2(L) and caspase-9 localized to the nucleus, correlating with chromatin.
• Caspase inhibition accelerated metaphase I to metaphase II transition; caspases localized to the meiotic spindle.
• Cleaved caspases were found in similar amounts in healthy and fragmented oocytes.
• Caspase inhibition did not prevent doxorubicin-induced apoptosis.

Conclusions:

• Cleaved caspases are present in oocytes before meiosis resumption.
• Caspases may play a regulatory role in oocyte maturation rather than being essential for doxorubicin-induced apoptosis.
• Further investigation is needed to fully understand the dispensability of caspases in oocyte death.