Localization of proteasomes in human oocytes and preimplantation embryos.

In the present study we describe the localization of proteasomes in human oocytes, apoptotic preimplantation embryos, and triploid preimplantation embryos by means of immunolabelling with the MCP21 monoclonal antibody detected by confocal microscopy. While in the oocytes proteasomes are scattered throughout the cytoplasm, in the pronuclear zygote they appear to concentrate at the periphery of the cytoplasm and do not enter the pronuclei. During early cleavage stages, proteasome immunolabelling is concentrated in the nuclei, while the examination of triploid blastocysts showed that proteasomes had a similar cellular distribution to somatic cell lines, i.e. in the nuclei but not in the nucleoli or the cytoplasm. It appears that the distribution of proteasomes dramatically changes during human preimplantation embryo development.