Igawa Takeshi

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  • Article
    Inbreeding ratio and genetic relationships among strains of the Western clawed frog, Xenopus tropicalis
    (Public Library of Science, 2015-07-29) Igawa, Takeshi ; Watanabe, Ai ; Suzuki, Atsushi ; Kashiwagi, Akihiko ; Kashiwagi, Keiko ; Noble, Anna ; Guille, Matthew ; Simpson, David E. ; Horb, Marko E. ; Fujii, Tamotsu ; Sumida, Masayuki
    The Western clawed frog, Xenopus tropicalis, is a highly promising model amphibian, especially in developmental and physiological research, and as a tool for understanding disease. It was originally found in the West African rainforest belt, and was introduced to the research community in the 1990s. The major strains thus far known include the Nigerian and Ivory Coast strains. However, due to its short history as an experimental animal, the genetic relationship among the various strains has not yet been clarified, and establishment of inbred strains has not yet been achieved. Since 2003 the Institute for Amphibian Biology (IAB), Hiroshima University has maintained stocks of multiple X. tropicalis strains and conducted consecutive breeding as part of the National BioResource Project. In the present study we investigated the inbreeding ratio and genetic relationship of four inbred strains at IAB, as well as stocks from other institutions, using highly polymorphic microsatellite markers and mitochondrial haplotypes. Our results show successive reduction of heterozygosity in the genome of the IAB inbred strains. The Ivory Coast strains clearly differed from the Nigerian strains genetically, and three subgroups were identified within both the Nigerian and Ivory Coast strains. It is noteworthy that the Ivory Coast strains have an evolutionary divergent genetic background. Our results serve as a guide for the most effective use of X. tropicalis strains, and the long-term maintenance of multiple strains will contribute to further research efforts.
  • Article
    Xenopus resources: Transgenic, inbred and mutant animals, training opportunities, and web-based support.
    (Frontiers Media, 2019-04-25) Horb, Marko E. ; Wlizla, Marcin ; Abu-Daya, Anita ; McNamara, Sean ; Gajdasik, Dominika ; Igawa, Takeshi ; Suzuki, Atsushi ; Ogino, Hajime ; Noble, Anna ; Robert, Jacques ; James-Zorn, Christina ; Guille, Matthew ; Nicolas, Morgane ; Lafond, Thomas ; Boujard, Daniel ; Audic, Yann ; Guillet, Brigitte ; Centre de Ressource Biologique Xenope team in France
    Two species of the clawed frog family, Xenopus laevis and X. tropicalis, are widely used as tools to investigate both normal and disease-state biochemistry, genetics, cell biology, and developmental biology. To support both frog specialist and non-specialist scientists needing access to these models for their research, a number of centralized resources exist around the world. These include centers that hold live and frozen stocks of transgenic, inbred and mutant animals and centers that hold molecular resources. This infrastructure is supported by a model organism database. Here, we describe much of this infrastructure and encourage the community to make the best use of it and to guide the resource centers in developing new lines and libraries.