Evidence that the voltage-dependent component in the fertilization process is contributed by the sperm

Area of Science:

• Reproductive Biology
• Developmental Biology
• Cellular Electrophysiology

Background:

• Fertilization involves complex molecular and electrical events.
• Voltage dependence of fertilization acts as an electrical block to polyspermy.
• Previous studies indicate varying degrees of voltage dependence across amphibian species.

Purpose of the Study:

• To elucidate the mechanisms underlying the voltage dependence of fertilization.
• To determine whether the egg or sperm contributes the voltage-dependent characteristic.
• To investigate the role of sperm in the electrical block to polyspermy.

Main Methods:

• Cross-fertilization experiments were conducted between three amphibian species with differing voltage dependence.
• Egg membrane potential was clamped at specific voltages (+40 mV, +50 mV, +20 mV) during fertilization attempts.
• Sperm from different species were used to fertilize eggs from species with known voltage-dependent or independent fertilization.

Main Results:

• Fertilization of Cynops eggs by Hynobius sperm was blocked at +40 mV, consistent with Hynobius sperm's voltage dependence.
• Fertilization between Bufo eggs and Hynobius sperm showed voltage dependence characteristic of Hynobius sperm, blocked at +50 mV but not +20 mV.
• These findings indicate that the sperm possesses the component responsible for voltage-dependent fertilization.

Conclusions:

• The voltage dependence of fertilization is primarily conferred by the sperm, not the egg.
• Sperm-derived factors are crucial for the electrical block to polyspermy.
• Understanding sperm's role in voltage dependence offers insights into fertilization control mechanisms.