Phorbol ester and sperm activate mouse oocytes by inducing sustained oscillations in cell Ca2+.

Area of Science:

• Reproductive Biology
• Cellular Signaling
• Developmental Biology

Background:

• Parthenogenetic activation of mouse oocytes involves a significant increase in intracellular calcium concentration ([Ca2+]i).
• The phorbol ester 12-O-tetradecanoyl phorbol acetate (TPA), a tumor promoter, activates cellular processes similar to those induced by elevated [Ca2+]i.

Purpose of the Study:

• To investigate the effect of TPA on intracellular calcium concentration ([Ca2+]i) in mouse oocytes.
• To determine if TPA can induce parthenogenetic activation in mouse oocytes.
• To compare the calcium signaling patterns induced by TPA with those observed during fertilization.

Main Methods:

• Measurement of intracellular calcium concentration ([Ca2+]i) using the photoprotein aequorin in mouse oocytes.
• Treatment of mouse oocytes with TPA to assess its parthenogenetic activating potential.
• Observation and recording of [Ca2+]i dynamics during TPA treatment and fertilization.

Main Results:

• TPA was found to be a potent parthenogenetic activating agent for mouse oocytes.
• Sustained oscillations in [Ca2+]i were observed in TPA-treated oocytes that subsequently underwent activation.
• Fertilization also induced sustained [Ca2+]i transients, continuing regularly for 4 hours, distinct from ethanol-induced activation.
• A component of the fertilization-induced calcium response appears related to TPA-induced oscillations.

Conclusions:

• TPA induces sustained calcium oscillations in mouse oocytes, leading to parthenogenetic activation.
• These TPA-induced calcium oscillations share characteristics with the sustained calcium transients observed during fertilization.
• TPA serves as a valuable tool for studying the mechanisms of calcium signaling in oocyte activation and fertilization.