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Toshihiko Eki

Affiliation Department of Environmental and Life Sciences
Title Professor / Chair of Department of Environmental and Life Sciences
Fields of Research Molecular Genetics / Molecular Biology / Functional Genomics
Degree PhD in Pharmaceutical Sciences (The University of Tokyo)
Academic Societies The Molecular Biology Society of Japan / The Pharmaceutical Society of Japan / The Japanese Biochemical Society / The Genetic Society of America
E-mail eki@ens
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Laboratory website URL


A number of chemicals or wastes are continuously produced by our social activities and are accumulated in the environment as well as in our bodies. These substances may be potentially and unexpectedly changed into genotoxic reagents, causing DNA damage to lead to regulatory dysfunctions of genetic information. Furthermore, it has been well known that excess DNA damage often shortens human lifespan mainly due to an increased risk of various cancers. The problem of "genome environment" is important in ecological life sciences as well as medical sciences. In addition, development of chemical sensing and environmental assessment technologies are in progress. So far, three research subjects have been carried out using model organisms S. cerevisiae and C. elegans by molecular, biochemical and genetic approaches. :
(1) Identification and characterization of novel nematode helicase-related proteins including DRH-3 that play roles in maintenance of genome integrity,
(2) Development of yeast-based assay systems for detecting genotoxicity and chemicals, and
(3) Analysis of soil nematodes by the DNA barcoding and development of C. elegans lifespan-based assay for ecotoxicants.

Theme1:Studies on a novel RNAi gene drh-3 involved in maintenance of genome integrity in C. elegans


We identified a novel nematode gene drh-3 that functions in both maintenance of chromosome integrity and RNA interference (RNAi). Since the relationship between RNAi and chromosome regulations has been largely unknown, we have focused on functional analyses of DRH-3 protein in C. elegans. This study will contribute to progress in basic biomedical sciences.

Recent publications:
◆Toshihiko Eki., Takeshi Ishihara, Isao Katsura, and Fumio Hanaoka: A genome-wide survey and systematic RNAi-based characterization of helicase-like genes in Caenorhabditis elegans. DNA Res., 14(4), 183-199 (2007)
◆Masaharu Nakamura, Rumi Ando, Taro Nakazawa, Takuro Yudazono, Naoko Tsutsumi, Naoki Hatanaka, Toshiyasu Ohgake, Fumio Hanaoka, Toshihiko Eki: Dicer-related drh-3 gene functions in germ line development by maintenance of chromosomal integrity in Caenorhabditis elegans. Genes Cells, 12(9), 997-1010 (2007)
◆Toshihiko Eki and Fumio Hanaoka: Discovery of orphan helicases and deorphanization by genome-wide analyses in two model organisms, S. cerevisiae and C. elegans, Bacterial DNA, DNA polymerase and DNA Helicases. pp.411-432, Nova Science Publishers (2010)


RNAi, C. elegans, genome integrity, drh-3 gene

Theme2:Development of biosensing assay systems using genetically altered yeasts


It is important to detect genome toxicities of chemicals and waste products. We have developed the biosensing assays by recombinant reporter yeasts for detecting genotoxicity. We also tried to develop recombinant yeasts that can be detect a broad range of chemicals.

Recent publications:
◆Kohei Ichikawa and Toshihiko Eki: A novel yeast-based reporter assay system for the sensitive detection of genotoxic agents mediated by a DNA damage-inducible LexA-GAL4 protein. J. Biochem., 139(1), 105-112 (2006)
◆Yukari Ochi, Harumi Sugawara, Mio Iwami, Megumi Tanaka and Toshihiko Eki: Sensitive detection of chemical-induced genotoxicity by the Cypridina secretory luciferase reporter assay using DNA repair-deficient strains of Saccharomyces cerevisiae. Yeast, 35(1), 265-278 (2011)


recombinant yeast, chmicals, genotoxicity

Theme3:Analysis of soil nematodes by molecular genetics approach and development of C. elegans lifespan-based assay for ecotoxicants


We have studied on soil nematodes by molecular biological approach for evaluating soil environment. We developed a novel lifespan-based assay for detecting biotoxicity of materials. This test will be useful for risk management of wasted chemicals because nematodes including C. elegans are majority of the living organisms in soil.

Recent publications:
◆Hiroaki Harada, Masaru Kurauchi, Rie Hayashi, and Toshihiko Eki: Shortened lifespan of nematode Caenorhabditis elegans after prolonged exposure to heavy metals and detergents. Ecotoxicology and Environmental Safety, 66(3), 378-383 (2007)
◆Masaru Kurauchi, Hisashi Morise, and Toshihiko Eki: Using the nematode Caenorhabditis elegans daf-16 mutant to assess the lifespan toxicity of prolonged exposure to ecotoxic agents. Journal of Health Science, 55(5), 796-804 (2009)
◆Toshihiko Eki:Ecotoxicology of free-living nematode Caenorhabiditis elegans, Ecotoxicology Around the Grobe, pp.1-52, Nova Science Publishers (2011)
◆Hisashi Morise, Erika Miyazaki, Shoko Yoshimitsu, and Toshihiko Eki: Profiling nematode communities in unmanaged flowerbed and agricultural field soils in Japan by DNA barcode sequencing. PLoS One, 7(12), e51785 (10 pages) (2012)

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