02643nas a2200157   4500008004100000245010600041210006900147260001200216490000700228520212200235100002102357700001802378700001902396700002002415856005002435       2012                        eng d00aComparative transcriptome analysis between planarian Dugesia japonica and other platyhelminth species0 aComparative transcriptome analysis between planarian Dugesia jap  c06/20120 v133 a<p>Background Planarians are considered to be among the extant animals close to one of the earliest groups of organisms that acquired a central nervous system (CNS) during evolution. Planarians have a bilobed brain with nine lateral branches from which a variety of external signals are projected into different portions of the main lobes. Various interneurons process different signals to regulate behavior and learning/memory. Furthermore, planarians have robust regenerative ability and are attracting attention as a new model organism for the study of regeneration. Here we conducted large-scale EST analysis of the head region of the planarian Dugesia japonica to construct a database of the head-region transcriptome, and then performed comparative analyses among related species. Results A total of 54,752 high-quality EST reads were obtained from a head library of the planarian Dugesia japonica, and 13,167 unigene sequences were produced by de novo assembly. A new method devised here revealed that proteins related to metabolism and defense mechanisms have high flexibility of amino-acid substitutions within the planarian family. Eight-two CNS-development genes were found in the planarian (cf. C. elegans 3; chicken 129). Comparative analysis revealed that 91% of the planarian CNS-development genes could be mapped onto the schistosome genome, but one-third of these shared genes were not expressed in the schistosome. Conclusions We constructed a database that is a useful resource for comparative planarian transcriptome studies. Analysis comparing homologous genes between two planarian species showed that the potential of genes is important for accumulation of amino-acid substitutions. The presence of many CNS-development genes in our database supports the notion that the planarian has a fundamental brain with regard to evolution and development at not only the morphological/functional, but also the genomic, level. In addition, our results indicate that the planarian CNS-development genes already existed before the divergence of planarians and schistosomes from their common ancestor.</p>
1 aNishimura, Osamu1 aHirao, Yukako1 aTarui, Hiroshi1 aAgata, Kiyokazu  uhttp://www.biomedcentral.com/1471-2164/13/289