Expression of survivin in human oocytes and preimplantation embryos

Objective To determine whether [1] survivin is expressed in human oocytes and embryos; [2] embryos grown in vitro secrete survivin protein; and [3] survivin levels are correlated with embryo cleavage rates. Design Experimental. Setting University-affiliated IVF clinic. Patient(s) Couples undergoing IVF-ET cycles. Intervention(s) Conventional reverse transcriptase–polymerase chain reaction (PCR), real-time PCR, immunohistochemistry, Western blot on oocytes, embryos and control choriocarcinoma JEG-3 cells, and ELISA analysis of conditioned culture media. Main Outcome Measure(s) Detection of survivin mRNA and protein in oocytes and preimplantation embryos and in JEG-3 cancer cells. Detection of survivin concentrations in embryo culture media. Result(s) Survivin mRNA and protein were expressed during human oocyte maturation, from germinal vesicle to metaphase II stage, and throughout embryo development, from pronuclear stage to blastocyst stage. Survivin was localized predominantly in the cytoplasm of all cells examined and in the oocytes on the chromatin of metaphase chromosomes and midbodies. Western blot analysis of human oocyte and cancer cell extracts detected a full-length (primary) survivin band of 16.5 kDa. Survivin was also detected in conditioned media samples from embryo cultures and showed a positive correlation with embryo cleavage rates. Conclusion(s) Our data have demonstrated for the first time that human oocytes/embryos not only express but also secret survivin, suggesting that survivin may play an important role in human oogenesis and embryogenesis.