Sperm phospholipase Czeta from humans and cynomolgus monkeys triggers Ca2+ oscillations, activation and development of mouse oocytes

Abstract

ResearchFusion with a fertilizing spermatozoon induces the mammalian oocyte to undergo a remarkable series of oscillations in cytosolic Ca 2+ , leading to oocyte activation and development of the embryo. The exact molecular mechanism for generating Ca 2+ oscillations has not been established. A sperm-specific zeta isoform of phospholipase C (PLCζ) has been identified in mice. Mouse PLCζ triggers Ca 2+ oscillations in mouse oocytes and exhibits properties synonymous with the 'sperm factor' that has been proposed to diffuse into the oocyte after gamete fusion. The present study isolated the PLCζ homologue from human and cynomolgus monkey testes. Comparison with mouse and monkey PLCζ protein sequences indicates a shorter X-Y linker region in human PLCζ and predicts a distinctly different isoelectric point. Microinjection of complementary RNA for both human and cynomolgus monkey PLCζ elicits Ca 2+ oscillations in mouse oocytes equivalent to those seen during fertilization in mice. Moreover, human PLCζ elicits mouse egg activation and early embryonic development up to the blastocyst stage, and exhibits greater potency than PLCζ from monkeys and mice. These results are consistent with the proposal that sperm PLCζ is the molecular trigger for egg activation during fertilization and that the role and activity of PLCζ is highly conserved across mammalian species.

Activation and Development of Pig Oocytes after Microinjection of Crude Sperm Extract

“…The latter hypothesis, on the other hand, proposes that after membrane fusion spermatozoa introduce a factor into the oocyte cytoplasm that has Ca 2+ -releasing ability. In recent studies, a novel sperm-specific isoform of PLC, named PLCζ, has been identified as the factor, and it has been reported that microinjection of complementary RNA for PLCζ from mouse, hamster, human and monkey spermatozoa elicits Ca 2+ oscillations in mouse oocytes equivalent to those seen during fertilization in mice [31,32]. Our results may support the sperm-factor hypothesis.…”

Role of Src homology 2 domain-mediated PTK signaling in mouse zygotic development

“…For example, while mammalian eggs express Fyn, Yes, and in some cases, Src (Talmor et al 1998, Talmor-Cohen et al 2004a), the results of two different studies indicate that these kinases are not required for the unique sperm-induced calcium oscillations (Kurokawa et al 2004a, Mehlmann & Jaffe 2005, which trigger egg activation in mammals (Carroll 2001). Instead, these calcium oscillations are triggered directly by a sperm-borne phospholipase that does not require PTK regulation (Cox et al 2002). The role of Src-family PTKs in later stages of mammalian fertilization has been addressed primarily using parthenogenetic activation.…”

PAWP, a Sperm-specific WW Domain-binding Protein, Promotes Meiotic Resumption and Pronuclear Development during Fertilization

“…tr-kit appears to activate the oocyte via a Fyn-phospholipase C␥1-mediated signaling pathway (13,14); a similar pathway has also been established in echinoderm and ascidian eggs (15). The discovery of the sperm-specific phospholipase C, on the other hand, offered the possibility that a phospholipase C protein of paternal origin was directly involved in triggering Ca 2ϩ oscillations during oocyte activation (16,17).…”