2005 Fiscal Year Final Research Report Summary
Contribution of transposable elements to spontaneous mutation rates in medaka fish
| Project/Area Number |
16570002
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Genetics/Genome dynamics
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| Research Institution | Nagoya University |
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Principal Investigator |
KOGA Akihiko Nagoya Univ., Sch.of Science, Associate professor, 大学院・理学研究科, 助教授 (80192574)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMA Akihiro Univ.Tokyo, Sch.of Frontier Sciences, Professor Emeritus, 大学院・新領域創成科学研究科, 名誉教授 (60011590)
KANAMORI Akira Nagoya Univ., Sch.of Science, Research associate, 大学院・理学研究科, 助手 (40324389)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Transposon / Transposition / Spontaneous mutation / Mutation rate / Medaka / Vertebrates |
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| Research Abstract |
The purpose of this research was to obtain experimental, direct evidence for our inference that transposition of transposable elements contributes to spontaneous mutations in the medaka fish. We used the i^b albion strain, which exhibits a quasi-albino phenotype due to insertion of a copy of the Tol2 transposable element in a pigmentation gene. We made single-pair crosses of this strain and analyzed changes in chromosomal locations of Tol2 copies over generations by Southern blot analysis, obtaining an estimate of 0.65 (copies/gamete/generation) for the transposition frequency. This high frequency is comparable to those realized with other highly active elements such as the Drosophila P element. We then screened embryos for mutant phenotypes. The estimated spontaneous mutation rate was as high as 0.22 (new mutations/gamete/generation), representing a 1,000-fold increase from spontaneous mutation rates so far determined with the same organism. Molecular analysis of new mutant genes revealed them to have been caused mostly by transposition of the Tol2 element. These results are a clear example of positive correlation of the transposition frequency and the spontaneous mutation rate. The results raise the possibility that the impact of DNA-based transposable elements on vertebrate genomes may be, and may have been, larger than generally postulated.
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