1994 Fiscal Year Final Research Report Summary
DIFFERENTIATION OF MEGAKARYOCYTES AND MECHANISMS OF CELL : ENDOMITOSIS AND CYCLIN
| Project/Area Number |
05670895
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hematology
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| Research Institution | CHIBA UNIVERSITY |
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Principal Investigator |
SATO Takeyuki CHIBA UNIVERSITY,PEDIATRICS, 医学部, 講師 (30187207)
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| Co-Investigator(Kenkyū-buntansha) |
MIURA Nobuyuki CHIBA UNIVERSITY,PEDIATRICS, 医学部, 医員
KAKUDA Harumi CHIBA UNIVERSITY,PEDIATRICS, 医学部, 医員
YOKOE Hidetaka CHIBA UNIVERSITY,ORALSURGERY, 医学部, 助手 (70261930)
FUSE Akira NIH,, 室長
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| Project Period (FY) |
1993 – 1994
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| Keywords | Megakaryocyte / Endomitosis / Cell cycle / Cyclin / K252a / Ploidy / Cell line |
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| Research Abstract |
Megakaryoblasts have a distinct feature that only DNA ploidy increase without mitosis (endomitosis). However, the physiological meaning and the process are obscure. SO we study about endomitosis of megakaryocytes using megakaryocytic cell lines, CMK and HEL.
HEL cells can be differentiated to megakaryocyte by stimulation of a protein kinase K252a or a phorbol-ester TPA.HEL cells treated with K252a for 4 days showed a noticeable increase in the proportion of polyploidy cells, cellular size and nuclear size. When K252a were added at G1/S boundary phase in the culture of HEL cells synchronized by 1mM hydroxyurea treatment, HEL cells were not inhibited the first and second round DNA synthesis, but inhibited cell division after first round S phase completely. On the other hand, TPA delayd the first round DNA synthesis, and blocked the cell division and the second round S phase completely. K252a did not inhibited the expression of cyclin B,cdc2 and cdc25B in the first round S phase, but TPA delayd the expression of the genes. These results suggested that K252a induced the polyploidization mainly by inhibiting mitosis of HEL cells. TPA may induced the multi-nucleation through different mechanism.
Several sublines that have ploidies of 2N and 4N were cloned from CMK cells. These sublines have the different stages of differentiation estimated by the expressions of surface glycoproteins IIb/IIIa Studies are ongoing to clarify the mechanisms of endomitosis by using these subclones.
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