Qualitative changes in protein synthesis associated with polyspermic fertilization of human eggs

To investigate the early molecular events in human oocytes that are triggered by fertilization, the authors examined the pattern of polypeptides synthesized by unfertilized and dispermic embryos obtained through an in vitro fertilization and embryo transfer (IVF-ET) program. Compared with unfertilized oocytes of the same postovulatory age, the de novo protein synthesis in tripronuclear dispermic zygotes (21 hours postinsemination) was characterized by the appearance of three novel protein bands with molecular weights of 41.2, 35.3, and 26.0 kD. Concomitant with these changes, these zygotes showed the disappearance of bands at 54.0, 36.5, and 28.0 kD, along with the decreased synthesis of a protein band at 42.5 kD. Although 24% of the aged unfertilized oocytes exhibited bands corresponding to 41.2 and 35.3 kD, the 26.0 kD protein is restricted to the tripronuclear embryos. The significance of these results is discussed in relation to the use of polyspermic human oocytes as a model for the study of the early molecular events triggered by fertilization.