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Phosphorylation of mitogen-activated protein kinase cascade during early embryo development in the mouse
N Iwamori1, K Naito, K Sugiura
1Laboratory of Applied Genetics, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan. aa07157@mail.ecc.u-tokyo.ac.jp
Abstract:
The mitogen-activated protein kinase (MAPK) cascade is one of the most important signal transduction pathways that regulate the cell cycle in somatic cells. The present study examined the phosphorylation states of components in the MAPK cascade, Raf-1, MEK-1, and extracellular signal regulated kinases (ERKs), which are activated by mitogens, throughout early mouse embryo development and in cultured somatic cells generally. In somatic cells, Raf-1 and MEK-1 were phosphorylated at M-phase and dephosphorylated during interphase. ERKs were not phosphorylated at any stage during the cell cycle. These results were similar to previous findings for the first and second cell cycles of early mouse embryos. In contrast, after the four-cell stage, not only ERKs, but also Raf-1 and MEK-1, were not phosphorylated at any stage during the cell cycle in mouse early embryos. These results suggest that the MAPK cascade in mouse embryos is regulated by the same mechanism as in somatic cells before the two-cell stage, and that regulation is changed to an embryo-specific mechanism after the four-cell stage.
Insights
The mitogen-activated protein kinase (MAPK) cascade regulates cell cycles. In early mouse embryos, MAPK regulation shifts from a somatic cell-like mechanism to an embryo-specific one after the four-cell stage.
Area of Science:
- Cell Biology
- Developmental Biology
- Signal Transduction
Background:
- The mitogen-activated protein kinase (MAPK) cascade is crucial for cell cycle regulation in somatic cells.
- Components like Raf-1, MEK-1, and extracellular signal-regulated kinases (ERKs) are key players in this pathway.
Purpose of the Study:
- To investigate the phosphorylation status of MAPK cascade components (Raf-1, MEK-1, ERKs) during early mouse embryonic development.
- To compare MAPK cascade regulation in early mouse embryos with that in cultured somatic cells.
Main Methods:
- Analysis of phosphorylation states of Raf-1, MEK-1, and ERKs.
- Comparison across different cell cycle stages in cultured somatic cells and early mouse embryos (up to the four-cell stage and beyond).
Main Results:
- In somatic cells, Raf-1 and MEK-1 are phosphorylated during M-phase and dephosphorylated during interphase; ERKs remain unphosphorylated.
- Early mouse embryos show similar patterns for the first two cell cycles.
- After the four-cell stage, Raf-1, MEK-1, and ERKs are not phosphorylated at any cell cycle stage in mouse embryos.
Conclusions:
- The MAPK cascade in mouse embryos is regulated similarly to somatic cells before the two-cell stage.
- A transition to an embryo-specific regulatory mechanism for the MAPK cascade occurs after the four-cell stage in mouse development.