| dc.description.abstract |
The mitogen-activated protein kinase (MAPK) cascade is one of the mostimportant signal transduction pathways that regulate the cell cycle in somaticcells. The present study examined the phosphorylation states of components inthe MAPK cascade, Raf-1, MEK-1, and extracellular signal regulated kinases(ERKs), which are activated by mitogens, throughout early mouse embryodevelopment and in cultured somatic cells generally. In somatic cells, Raf-1and MEK-1 were phosphorylated at M-phase and dephosphorylated duringinterphase. ERKs were not phosphorylated at any stage during the cell cycle.These results were similar to previous findings for the first and second cellcycles of early mouse embryos. In contrast, after the four-cell stage, notonly ERKs, but also Raf-1 and MEK-1, were not phosphorylated at any stageduring the cell cycle in mouse early embryos. These results suggest that theMAPK cascade in mouse embryos is regulated by the same mechanism as in somaticcells before the two-cell stage, and that regulation is changed to anembryo-specific mechanism after the four-cell stage. |
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