Int. J. Dev. Biol. 52: 585 - 594 (2008)

https://doi.org/10.1387/ijdb.072530ks

Vol 52, Issue 5-6

Special Issue: Fertilization

The dynamics of calcium oscillations that activate mammalian eggs

Open Access | Published: 1 July 2008

Karl Swann* and Yuansong Yu

Department of Obstetrics and Gynaecology, School of Medicine, Cardiff University, Cardiff, UK

Abstract

It has been known for some time that mammalian eggs are activated by a series of intracellular calcium oscillations that occur shortly after sperm egg membrane fusion. Recent work has identified a novel sperm specific phospholipase C zeta as the likely agent that stimulates the calcium oscillations in eggs after sperm-egg membrane fusion. PLCzeta is stimulated by low intracellular calcium levels in a manner which suggests that there is a regenerative feedback of calcium release and PLCzeta induced inositol 1,4,5-trisphophate (InsP₃) production in eggs. This implies calcium oscillations in fertilizing mammalian eggs are driven by underlying oscillations of InsP₃. This model of oscillations is supported by the response of mouse eggs to sudden increases in InsP₃. The cellular targets of calcium oscillations include calmodulin-dependent protein kinases, protein kinase C and mitochondria. There is evidence that eggs might be best activated by multiple calcium increases rather than a single calcium rise. As yet we do not fully understand how the target of calcium in a mammalian egg might decode the patterns of calcium changes that can occur during egg activation.

Keywords

fertilization, egg, sperm, calcium, oscillations