| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Shosei Osaka Univetsity, IMCB Investigator, 細胞生体工学センター, 助手 (60294138)
TAKEDA Sin-ichi National Institute of neuroscience, Section Chief, 神経センター・神経研究所遺伝子工学, 室長 (90171644)
FUJISAWA Atsuko National Institute of neuroscience, Section Chief, 神経センター・神経研究所遺伝子工学, 室長 (60209038)
NABESHIMA Yo-ichi National Institute of neuroscience, Director (60108024)
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| Research Abstract |
1) LPA and bFGF control different modes in proliferating myoblasts We discoverd that LPA stimulates the growth and inhibits the differentiation of mouse C2C12 myoblasts cells, in a distinct manner from bFGF whose mitotic and anti-differentiation actions have been well investigated. These actions of LPA were involvement of Gi class of G proteins, whereas bFGF acts through receptor tyrosine kinases. LPA and bFGF act differently in regulating the myogenic bHLH proteins. LPA stimulates the proliferation of undifferentiated myoblasts allowing the continued expression of MyoD,but in contrast, bFGF does so with the MyoD expression suppressed at the mRNA level. Both compounds maintain the myf-5 expression and suppress the myogenin expression. In addition, while LPA did not inhibit cell-cell contact-induced differentiation. bFGF strongly inhibited process.
2) Variation of MyoD and Myf-5 specifies the differentiating and Reserve cells upon myogenesis. We investigated that homogeneously growing C2
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C12 mouse myoblasts generate two distinct types of subpopulatioin upon serum deprivation ; differentiating cells and reserve cells. A number of events known to be related to terminal differentiation including myogenin expression, biochemical differentiation, permanent withdrawal from cell cycle which is parallel to P21^<WAF1> expression, and cell fusion, occur only in the former type of cells. In contrast, the latter do not cause these events and remain undifferentiated. However, they retain their myogenic potentials and cause differentiation identically to the original myoblasts after serum re-stimulation.
These two cell types are distinguishable in very early step of differentiation by MyoD and Myf-5 expression. Whereas the differentiating cells continue to express MyoD and Myf-5, the reserve cell rapidly lose or decrease their expression. This variation proceeds the myogenin expression. Moreover, ectopic expression of MyoD pretein converts the reserve cells to differentiating cells. indicating that MyoD specifies the cells to differentiate. Less
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