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Updated: Aug 25, 2026

Medium-throughput Screening Assays for Assessment of Effects on Ca2+-Signaling and Acrosome Reaction in Human Sperm
Published on: March 1, 2019
The cytosolic sperm factor that triggers Ca2+ oscillations and egg activation in mammals is a novel phospholipase C:
K Swann1, M G Larman, C M Saunders
1Department of Anatomy and Developmental Biology, University College London, London WC1E 6BT, UK. ucgakas@ucl.ac.uk
Abstract:
When sperm activate eggs at fertilization the signal for activation involves increases in the intracellular free Ca2+ concentration. In mammals the Ca2+ changes at fertilization consist of intracellular Ca2+ oscillations that are driven by the generation of inositol 1,4,5-trisphosphate (InsP3). It is not established how sperm trigger the increases in InsP3 and Ca2+ at fertilization. One theory suggests that sperm initiate signals to activate the egg by introducing a specific factor into the egg cytoplasm after membrane fusion. This theory has been mainly based upon the observation that injecting a cytosolic sperm protein factor into eggs can trigger the same pattern of Ca2+ oscillations induced by the sperm. We have recently shown that this soluble sperm factor protein is a novel form of phospholipase C (PLC), and it is referred to as PLCzeta(zeta). We describe the evidence that led to the identification of PLCzeta and discuss the issues relating to its potential role in fertilization.
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