A new ovulation inducing factor of sea cucumber

Research Project

Project/Area Number	16K07424
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Research Field	Morphology/Structure
Research Institution	Kyushu University
Principal Investigator	Yoshikuni MIchiyasu 九州大学, 農学研究院, 教授 (50210662)
Project Period (FY)	2016-04-01 – 2019-03-31
Project Status	Completed (Fiscal Year 2018)
Budget Amount *help	¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000) Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000) Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000) Fiscal Year 2016: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Keywords	棘皮動物 / 排卵 / 卵成熟 / 生殖 / 生理活性物質 / ナマコ / 排卵誘発因子 / 比較内分泌
Outline of Final Research Achievements	We found a new biological factor to induce ovulation of sea cucumber, Apostichopus japonicus and Holothuria leucospilota. The factor did not induce any oocyte maturation and induced ovulation of oocytes without resumption of meiosis. The factor was found in an incubation medium where eggs and sperms were released from stimulated gonads. The factor was an ionic compound with a molecular size less than 10,000 Da estimated by methods of ultrafiltration and gel filtration chromatography. It was able to be separated by a reverse-phased HPLC. We also found that a serine protease inhibitor, AEBSF(4-(2-aminoethyl) benzensulfonyl fluoride), induced ovulation without oocyte maturation at 1 mM. Released oocytes retained nuclei and looked as normal. It may indicate that there is some mechanism to initiate ovulation process independent from a physiological state of oocytes. It is still unclear whether a site of action of AEBSF is similar to that of the ovulation-inducting factor found in the study.
Academic Significance and Societal Importance of the Research Achievements	排卵現象は、卵巣内の卵が卵成熟誘起ホルモンの作用で減数分裂を再開し、受精可能となった卵が濾胞組織から放出されることである。減数分裂を再開しない卵（未成熟卵）は排卵されないことから、排卵後に精子と出会う卵は全て受精可能であることを保証する機構と言える。しかし、排卵を始動させる仕組みについては何も判っていない。本課題で、卵の減数分裂の再開の有無に関わらず、排卵機構のみを刺激する活性因子が卵巣組織中に存在することを明らかにした。その化学的実体が判れば、その作用機構の解析を手掛かりに排卵現象の制御機構を明らかにすることが可能となり、排卵異常等の病態の解明が可能となる。