Phospholipase Cζ rescues failed oocyte activation in a prototype of male factor infertility

Objective: To determine the effect of infertility-linked sperm phospholipase C zeta (PLC zeta) mutations on their ability to trigger oocyte Ca2+ oscillations and development, and also to evaluate the potential therapeutic utility of wild-type, recombinant PLC zeta protein for rescuing failed oocyte activation and embryo development. Design: Test of a novel therapeutic approach to male factor infertility. Setting: University medical school research laboratory. Patient(s): Donated unfertilized human oocytes from follicle reduction. Intervention(s): Microinjection of oocytes with recombinant human PLC zeta protein or PLC zeta cRNA and a Ca2+ sensitive fluorescent dye. Main Outcome Measure(s): Measurement of the efficacy of mutant and wild-type PLC zeta-mediated enzyme activity, oocyte Ca2+ oscillations, activation, and early embryo development. Result(s): In contrast to the wild-type protein, mutant forms of human sperm PLC zeta display aberrant enzyme activity and a total failure to activate unfertilized oocytes. Subsequent microinjection of recombinant human PLC zeta protein reliably triggers the characteristic pattern of cytoplasmic Ca2+ oscillations at fertilization, which are required for normal oocyte activation and successful embryo development to the blastocyst stage. Conclusion(s): Dysfunctional sperm PLC zeta cannot trigger oocyte activation and results in male factor infertility, so a potential therapeutic approach is oocyte microinjection of active, wild-type PLC zeta protein. We have demonstrated that recombinant human PLC zeta can phenotypically rescue failed activation in oocytes that express dysfunctional PLC zeta, and that this intervention culminates in efficient blastocyst formation. (Fertil Steril (R) 2013;99:76-85. (C) 2013 by American Society for Reproductive Medicine.)