The Fertilization Calcium Signal and How it is Triggered

Abstract

Publisher Summary This chapter describes how the calcium transient is detonated by the sperm, how it spreads so rapidly through the egg, and how it is that a transient increase in Ca i leads to progression into the cell cycle. It turns out that calcium waves of the sort that were first seen in eggs are a general property of calcium signaling systems in somatic cells too. Calcium signaling systems have built into them positive feedback mechanisms that give rise to spatial waves and temporal oscillations of free calcium concentration when the signaling system is stimulated by a fixed amount of external agonist. The waves and oscillations are two sides of the same coin. The unifying feature of calcium waves and oscillations is that they primarily involve the modulated release and reuptake of calcium from intracellular stores. The site of calcium release and resequestration is generally accepted to be the endoplasmic reticulum. Eggs provide beautiful examples of calcium waves and oscillations. Hamster eggs experience both calcium waves and calcium oscillations at fertilization. The multiple calcium transients after fertilization in hamster eggs can be reproduced with varying degrees of fidelity by artificial activating agents.