title: Unusually Large Number of Mutations in Asexually Reproducing Clonal Planarian Dugesia japonica.
abstract: We established a laboratory clonal strain of freshwater planarian (Dugesia japonica) that was derived from a single individual and that continued to undergo autotomous asexual reproduction for more than 20 years, and we performed large-scale genome sequencing and transcriptome analysis on it. Despite the fact that a completely clonal strain of the planarian was used, an unusually large number of mutations were detected. To enable quantitative genetic analysis of such a unique organism, we developed a new model called the Reference Gene Model, and used it to conduct large-scale transcriptome analysis. The results revealed large numbers of mutations not only outside but also inside gene-coding regions. Non-synonymous SNPs were detected in 74% of the genes for which valid ORFs were predicted. Interestingly, the high-mutation genes, such as metabolism- and defense-related genes, were correlated with genes that were previously identified as diverse genes among different planarian species. Although a large number of amino acid substitutions were apparently accumulated during asexual reproduction over this long period of time, the planarian maintained normal body-shape, behaviors, and physiological functions. The results of the present study reveal a unique aspect of asexual reproduction.
authors.affiliation: Global COE Program: Evolution and Biodiversity, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.|Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishimura
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Hosoda
authors.affiliation: Global COE Program: Evolution and Biodiversity, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Kawaguchi
authors.affiliation: Global COE Program: Evolution and Biodiversity, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.|Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.|Cellular and Structural Physiology Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan.
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yazawa
authors.affiliation: Center for Developmental Biology, RIKEN, 2-2-3 Minatojima-Nakamachi, Chuo-ku, Kobe, Hyogo, Japan.|Advanced Center for Computing and Communication, RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan.
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Umesono
authors.affiliation: Global COE Program: Evolution and Biodiversity, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.|Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Agata
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002452:Cell Count; D002999:Clone Cells; D015870:Gene Expression; D020869:Gene Expression Profiling; D049751:Genome, Helminth; D015801:Helminth Proteins / Q000235:genetics*; D008957:Models, Genetic; D058977:Molecular Sequence Annotation; D009154:Mutation; D016366:Open Reading Frames; D010932:Planarians / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012100:Reproduction, Asexual / Q000235:genetics*; D059467:Transcriptome
chemical_list: D015801:Helminth Proteins