Nuclear translocation of nuclear factor kappa B in early 1-cell mouse embryos

Nuclear factor kappa B (NF-kappa B) is a transcription factor that controls the expression of a number of genes under cellular redox potential, It has recently been found that NF-kappa B plays a pivotal role in morphogenesis and embryonic development, e.g., in formation of Drosophila malanogaster ve ntral structures and chicken limb buds. However, the role of NF-kappa B in preimplantation development in mammals is not yet understood. In this study , we show that RelA, one of the subunits of NF-kappa B, is expressed in mou se eggs and embryos from the metaphase II (MII) oocyte to the blastocyst st age. Therefore, it is thought that RelA is maternally expressed and that it continues to be expressed during preimplantation development. Immunofluore scence analysis showed that RelA protein was mainly distributed in the cyto plasm of embryos, whereas nuclear translocation of RelA, evidence for NF-ka ppa B activation, was observed only at the early 1-cell stage. Finally we s tudied the effects of NF-kappa B inhibitors, pyrrolidine dithiocarbamate an d N-acetyl-L-cysteine, on the preimplantation development of mouse embryos. When these inhibitors were added to the culture medium from the early 1-ce ll stage, subsequent development through tbe 2-cell stage was inhibited. Ho wever, little, if any, influence on the progression through the 2-cell stag e was observed when the inhibitors were added at the late 1-cell or the 2-c ell stage. Taken together, the results suggest that the activation of NF-ka ppa B at the early 1-cell stage is required for the development of mouse em bryos beyond the 2-cell stage.