A study on medaka ovulation with an emphasis on the relation with oocyte maturational event

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04810
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Morphology/Structure
• Research Institution: Hokkaido University
• Principal Investigator: Takahashi Takayuki 北海道大学, 理学研究院, 名誉教授 (80197152)
• Co-Investigator(Kenkyū-buntansha): 荻原 克益 北海道大学, 理学研究院, 准教授 (00422006)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: メダカ / 排卵 / 卵成熟 / ギャップ結合

Outline of Final Research Achievements

The purpose of this project was to examine whether ovualtion and oocyte maturation, which are both triggered by the ovulatory surge of LH in vertebrates, would be closely linked, and if any, what would be the mechanism by which the two processes occur in harmony? To this end, we used an in vitro ovulation system established for medaka ovarian follicles. Assuming that gap junctional communication between follicle cells and the oocyte and/or between two neighboring follicle cells might play an important role in ovulating follicles, we examine the effect of gap junction blockers on ovulation and oocyte maturation. In vitro follicle ovulation, but not oocyte maturation, was strongly inhibited by the blockers. The inhibition of follicle ovulation by gap junction blockers was demonstrated to be accompanied by the inhibition of MT2-MMP expression. In addition, we suggest that several connexin species may be involved in the gap junctional communication for successful ovulation.

Free Research Field

生殖生物学

Academic Significance and Societal Importance of the Research Achievements

生殖生物学の重要課題のひとつである排卵現象は，これまで主に哺乳類を用いて活発に研究されてきた。100年以上の長い研究の歴史を背景に膨大な知見が蓄積されているが，今なお多くの未解明の課題が残されている。近年になって、魚類を用いた排卵研究が展開されるようになり，脊椎動物の排卵に共通するメカニズムがあることが明らかになった。脊椎動物の排卵研究で残された大きな課題は卵成熟と排卵の連関性の解明である。本研究成果は，我国発祥のモデル生物であるメダカを用いて，「排卵と卵成熟はどのように連関するのか？」という永年の疑問の解明に資するものである。