| Research Abstract |
In vitro development of mammalian embryos during preimplantation period from the 1-cell to the blastocyst stages is known to be arrested at a stage characteristics for the species when zygotic gene activation (ZGA) occurs. This developmental arrest might, therefore, reflect a ZGA that is not well-regulated under in vitro culture conditions. Recently, involvement of reactive oxygen species (ROS) in this developmental arrest has been noted. Lowering oxygen tension and the addition of anti-oxidants, such as superoxide dismutase or thioredoxin, to the culture medium has been shown to exert a beneficial effect on in vitro development of embryos. Thus, it is much of interest to define the mechanisms by which early embryonic development is regulated by ROS.Recently, it has become clear that ROS have additional functions besides oxidative stress as second messengers for regulation of cell growth and differentiation. In the present studies, attempts were made to define the redox regulation in i
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n vitro development of early mouse embryos. As the results, it was shown that the mRNA and protein of nuclear factor kappa B (NF-kB), a transcription factor that controls the expression of a number of genes under cellular redox potentials, are expressed in mouseembryos during preimplantation development, and NF-kB is stage-specifically activated at early 1-cell stage in mouse embryos, and moreover that the activation of NF-kB is essential for the development of mouse embryos beyond the 2-cell stage. During the course of experiments on the production of antibodies that recognize specifically activated form of NF-kB, we found NF-kB-related 100 kDa protein. Cloning experiments of the protein revealed that it is a novel pre-mRNA splicing factor in mammals, and immunofluorescense experiments revealed that it is also stage -specifically accumulated in the nuclei of late 1-cell mouse embryos. In the second experiments, we found that nitric oxide, a free radical molecule acts as a regulator of development, especially transition of 2-cell embryos to the 4-cell stage and formation of blastocysts. Thus, it is indicated that the development and gene expression of embryos during preimplantation stages, especially at periods of ZGA and blastocyst formation are regulated under redox controls. Less
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