1995 Fiscal Year Final Research Report Summary
Mechanism of fertilization in the ascidian, Ciona intestinalis.
| Project/Area Number |
06044023
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Tohoku University |
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Principal Investigator |
KYOZUKA Keiichiro Tohoku Univ. Faculty of Science, Assistant Prof., 理学部, 助手 (40124573)
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| Co-Investigator(Kenkyū-buntansha) |
TOSTI Elisabetta Stazione Zoologica, Napoli Investigator, Researcher, 細胞生物部門, 研究員
DALE Brian Stazione Zoologica, Napoli Investigator. Prof., 細胞生物部門, 教授
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| Project Period (FY) |
1994 – 1995
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| Keywords | Ciona interstinalis / Fertilization / Meiosis / Cell cycle / Intracellular calcium / M-phase promoting factor / Sperm factor / Calcium oscillation |
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| Research Abstract |
The interaction between calcium signaling and cell cycle control was studied during meiotic progression in ascidian Ciona intestinalis. We measured intracellular Ca^<2+> in oocytes at fertilization and during progression through meiosis. The inttacellular calcium concentration increased shortly after insemination in a single transient. and this was followed by several smaller oscillations that lasted for approximately 5 min (phase 1). The first polar body was extruded after the completion of oscillations. about 9 min after insemination. The intracellular calcium level remained at baseline for a period of 5 min (phase 2). At 14 min post insemination a second series of oscillations was initiated that lasted 11 min (phase 3). and terminated at the time of second polar body extrusion. In many deuterostomes. oocyte activation is accompanied by a large single calcium transient. This transient increase in calcium is thought to play a key role in the cells decision to EXIT the cell cycle ; however, the interaction of this calcium signal with M-phase promoting factor (MPF). cytostatic factor (CSF) and the other events leading to the completion of meiosis have not been resolved. Injection of BAPTA during phase 2 suppressed the Phase 3 calcium transients, and inhibited both the increase in III kinase activity normally encountered at metaphase II.and second polar body extrusion.
To study how sperm trigger the egg activation. sperm extract was prepared and injected to Ciona oocyte. Injection of sperm extract mimicked the ferilization by sperm and induced both the calcium transients and second polar body extrusion. The result indicates that sperm has factor (s) which induces calcium transients and egg activation in Ciona oocytes and works directly in the egg eytoplasm.
The ascidian oocyte is an interesting model to study cell cycle regulation in meiosis.
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