Alterations of PLCβ1 in mouse eggs change calcium oscillatory behavior following fertilization

Inositol 1,4,5-trisphosphate generated by the action of a phospholipase C (PLC) mediates release of intracellular Ca2+ that is essential for sperm-induced activation of mammalian eggs. Much attention currently focuses on the role of sperm-derived PLC in generating changes in egg intracellular Ca2+ despite the fact that PLC zeta constitutes a very small fraction of the total amount of PLC in a fertilized egg. Eggs express several isoforms of PLC, but a role for an egg-derived PLC in sperm-induced Ca2+ oscillations has not been examined. Reducing egg PLC beta 1 I by a transgenic RNAi approach resulted in a significant decrease in Ca2+ transient amplitude, but not duration or frequency, following insemination. Furthermore, overexpressing PLC beta 1 by microinjecting a Plc beta 1 cRNA significantly perturbed the duration and frequency of Ca2+ transients and disrupted the characteristic shape of the first transient. These results provide the first evidence for a role of an egg-derived PLC acting in conjunction with a sperm-derived PLC zeta in egg activation. (C) 2007 Elsevier Inc. All rights reserved.