Molecular mechanisms underlying production of oocyte maturation inducing hormone in teleost

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H02275
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 40040:Aquatic life science-related
• Research Institution: Hokkaido University
• Principal Investigator: Ijiri Shigeho 北海道大学, 水産科学研究院, 准教授 (90425421)
• Co-Investigator(Kenkyū-buntansha): 足立 伸次 北海道大学, 水産科学研究院, 特任教授 (40231930) ; 柴田 安司 帝京科学大学, 生命環境学部, 准教授 (80446260)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 卵成熟誘起ホルモン / DHP / MIH / ティラピア / ウナギ / チョウザメ

Outline of Final Research Achievements

Maturation-inducing hormone in fish was identified as DHP. DHP is directly related to the maturational successful to produce fertilizable eggs. This study proved that Hsd17b12L is the enzyme to convert the precursor 17OHP to DHP throughout the fish evolution from sturgeon to eel, salmon and tilapia. Meanwhile, this study illustrated that DHP production is controlled by not only Hsd17b12L expression but also 17OHP production. Salmonid and medaka were controlled by Hsd17b12L expression, however sturgeon and eel were controlled by 17OHP production. 17OHP production is controlled by the balance of cyp17a1 and cyp17a2 expressions. This study has not reached to understand control mechanisms to regulate transcription of these genes. Toward understanding in MIS production control, transcriptional control of cyp17a1, cyp17a2 and hsd17b12L will be necessary to develop artificial maturation control for unmanageable fish species.

Free Research Field

魚類生殖生理学

Academic Significance and Societal Importance of the Research Achievements

絶滅が危惧される魚種では人が増殖を助ける必要がある。その際、受精可能な卵を得るには卵成熟をホルモン操作によって人為誘導する必要がある。卵成熟を誘起するDHPが適切な時期に卵巣で作られれば卵成熟する。飼育下の繁殖困難魚ではDHPが作られず産卵に至らない。ところが、DHP産生の分子機構は古くから間違った理解が広がっていた。本研究は、従来の説を完全に否定し、条鰭類を網羅した証拠を示して正しいDHP産生制御機構を初めて明らかにしたものである。本研究で扱う、ウナギやチョウザメなどで、人為卵成熟技術を正しく評価、発展させる分子的評価基盤を世界で初めて示すことができたものである。