1993 Fiscal Year Final Research Report Summary
M/lecular regulation of germ cell formation
| Project/Area Number |
02102010
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| Research Category |
Grant-in-Aid for Specially Promoted Research
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| Allocation Type | Single-year Grants |
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| Research Institution | Okazaki National Research Institutions |
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Principal Investigator |
NAGAHAMA Yoshitaka Okazaki National Research Institutions, National Institute for Basic Biology, Professor, 基礎生物学研究所, 教授 (50113428)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Tohru Okazaki National Research Institutions, National Institute for Basic Biology, As, 基礎生物学研究所, 助手 (30221972)
TANAKA Minoru Okazaki National Research Institutions, National Institute for Basic Biology, As, 基礎生物学研究所, 助手 (80202175)
YAMASHITA Masakane Okazaki National Research Institutions, National Institute for Basic Biology, As, 基礎生物学研究所(平成5年4月より北海道大学・理学部・助教, 助手 (30202378)
YOSHIKUNI Michiyasu Okazaki National Research Institutions, National Institute for Basic Biology, As, 基礎生物学研究所, 助手 (50210662)
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| Project Period (FY) |
1990 – 1993
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| Keywords | Fish / Germ cells / Hormone / Meiosis / Gonads / Cell cycle / Maturation-promoting factor (MPF) / Cell culture |
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| Research Abstract |
The molecular mechanism of germ cell formation, in particular spermatogenesis and oocyte maturation, has been investigated, using fish as a primary study model.
1) The cDNAs encoding 5 steroidogenic enzymes responsible for 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17a, 20b-DP, a common maturation-inducing hormone in fish) biosynthesis have been isolated and sequenced. We have shown that gonadotropin-induced 20beta-HSD mRNA expression is a prerequisite for 17a, 20b-DP production by granulosa cells. 2) We characterized specific binding of [^3H]17a, 20b-DP to plasma membranes from defolliculated oocytes of rainbow trout. A gonadotropin-induced increase in 17a, 20b-DP receptor concentrations is responsible for the development of oocyte maturational competence. Carp maturation-promoting factor (MPF) (cdc2 kinase and cyclin B) was purified and characterized. 17a, 20b-DP induces oocytes to synthesize cyclin B, which in turn activates preexisting cdc2 kinase through threonine phosphorylation (161) of cdc2 kinase by a threonine kinase (p40^<M015>). We discovered that cyclin degradation is triggered by limited proteolysis of cyclin B (Lys57) by active proteasome. 3) An organ culture system has been used to demonstrate that in the eel 11-ketotestosterone can induce all stages of spermatogenesis in vitro within 21 days. Our findings suggest that gonadotropin stimulates the Leydig cells to produce 11-ketotestosterone, which in turn activates the Sertoli cells to produce activin B.Activin B then acts on spermatogonia to induce mitosis leading to the formation of spermatocytes.
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