Abstract
Protein tyrosine kinases (PTKs) play pivotal roles in numerous cellular functions, i.e., differentiation, proliferation, and morphogenesis, in various types of cells. To reveal the role of PTK in the early preimplantation development, expression and function of PTK in the mouse embryos was examined. In this study, it has been shown that Jak2 is one of the dominantly expressed PTKs in MII stage oocytes. Jak2 protein was localized predominantly in female pronucleus in 1-cell embryos, but not male one. At MII stage and first mitosis, Jak2 was localized to the chromosomes. In culture cells that are known to be express Jak2, localization of Jak2 was detected in the cytoplasm, but not nucleus. Jak2-GFP fusion protein was also localized in cytoplasm of these culture cells, but was in the nucleus of 2-cell embryos. Endogenous Jak2 was not accumulated either in the transplanted nuclei of NIH3T3 or male pronuclei. These results showed that nuclear localization of Jak2 is not common phenomenon in the cells expressing Jak2 and accumulation of Jak2 onto the chromosome is regulated by some factor(s) associated with the chromatins. These results suggest a novel function of Jak2 in the regulation of early preimplantation development. [Jpn J Physiol 55 Suppl:S79 (2005)]
