2003 Fiscal Year Final Research Report Summary
Analysis of the 5S Ribosomal DNA Restricted to Germline Cenome in Myxiniformes
| Project/Area Number |
13640619
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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 |
遺伝
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| Research Institution | Toho University |
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Principal Investigator |
KUBOTA Souichirou Toho Univ., Faculty of science, Associate Prof., 理学部, 助教授 (30277347)
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| Project Period (FY) |
2001 – 2003
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| Keywords | Chromosome elimination / Myxiniformes / 55 rDNA |
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| Research Abstract |
It is known that in eight hagfishes chromosome elimination occurs during early embryogenesis.In this study, I isolated and investigated two types of 55 rDNA that are known to belong to multigene families : one type from somatic and the other from somatic and germ DNA in a Japanese hagfish Eptatretus burgeri.These two types of 5S rDNA had 911 nucleotide differences between them in the gene region(120 bp), and differed quite a lot in length and sequence in the NTS region.Southern blot hybridization and FISH analyses demonstrated that the germline type of 55 rDNA was restricted to the germline genome and was amplified abundantly there, while the somatic type was retained in both the somatic and germline genomes.Additionally, several pseudogenes of 55 rDNA amplified abundantly were also isolated from both the somatic and germline genomes.In order to investigate the transcriptional activity of the two types of 55 rDNA, we analyzed the cDNA sequence of 5S rRNA from somatic and germ tissues of E. burgeri.In the germ cells, the cDNA sequences were derived from both the germline and somatic types of 5S rDNA, while in the somatic cells ; they were derived exclusively from the somatic type.These results revealed that both types of 5S rDNA in E. burgeri had transcriptional activity ; implying that the dual 55 rDNA expression system in this species is regulated in the same way as has been reported for some amphibians and-pisces, through the phenomenon of chromosome elimination.Subsequent molecular cloning and sequence analysis revealed that the differentiation of the somatic and germline types of 5S rDNA among examined all eight hagfishes, implying that the dual 5S rDNA expression system is regulated through the phenomenon of chromosome elimination in Myxiniformes.
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