Practice question

Phospholipase C zeta is testis-specific soluble protein localized in perinuclear theca of mammalian sperm head, delivered into ooplasm upon membrane fusion. Uniquely active at basal calcium levels, it cleaves phosphatidylinositol 4,5-bisphosphate into IP3 and diacylglycerol, triggering calcium release from endoplasmic reticulum. Mice lacking PLC zeta show failure of calcium oscillations despite normal sperm penetration. Injection of recombinant PLC zeta cRNA restores activation. Therefore paternal contribution of this enzyme provides definitive trigger for oocyte activation, meiotic resumption, zinc spark initiation and initiation of embryonic development cascade and maternal mRNA recruitment.