| Budget Amount *help |
¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
To clarify the molecular mechanisms involved in germ cell differentiation during gametogenesis, the genes involved in controlling these specialized mitotic and meiotic cell cycles of germ cell differentiation must be identified and characterized. The eel testis provides powerful experimental models for investigating the regulatory mechanisms of spermatogenesis, because this model is completely regulated by hormonal induction. To understand the control mechanisms of spermatogenesis, we isolated several kinds of cell-cycle related gene cDNAs, and investigated the relationships between cell cycle-related gene products and gametogenesis in eel testes. After the hormonal induction of spermatogenesis, cyclin E2, A2, and B (B1, B2, B3) are expressed in spermatogonia sequentially. Dmc1 and cyclin A1 become expressed in spermatogenic cells sequentially during meiosis. Although Bl and B2 are expressed in spermatogenic cells from spermatogonia to spermatcytes, cyclin B3 expression is limited duri
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ng spermatogenesis to spermatogonia. The differences in the expression patterns and MPF activities among the B-type cyclins during spermatogenesis after hormonal initiation suggests that each B-type cyclin plays a distinct role in eel spermatogenesis, and that cyclin B3 is specifically involved in spermatogonial proliferation (mitosis), but not meiosis. To clarify the role of E-type cyclins during die initiation of spermatogenesis, we examined the effects of E-type cyclins on spermatogenesis in vitro by introducing E-type cyclins by means of electroporation into testis fragments before the induction of spermatogenesis. The introduction of E-type cyclins in this manner resulted in the initiation of spermatogenesis in vitro, without the need for hormonal induction of spermatogenesis. The initiation of spermatogenesis was accompanied by massive proliferation of type B spermatogonia. but not by self-renewal proliferation of type A spermatogonia, suggesting that an increase in cyclin E2 expression after the hormonal induction of spermatogenesis plays an important role in the shift of spermatogenic cell differentiation from stem cell renewal to active spermatogenesis. Less
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