Comparative transcriptome analysis between planarian Dugesia japonica and other platyhelminth species

Abstract

BackgroundPlanarians 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.ResultsA 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.ConclusionsWe 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.

Ca2+ channels and praziquantel: A view from the free world

“…Schistosomes therefore possess a smaller complement of voltage-gated cation influx channels for supporting excitable tissue physiology that exists in the free-living turbellarians. This narrow repertoire of voltage-gated channels, perhaps reflecting the massive gene loss associated with the evolution of parasitism [35, 91], provides opportunity for chemotherapeutic attack and highlights the need for understanding the molecular basis of neuronal and tissue excitability in these pathogens that is clearly divergent from their hosts.…”

Girardia dorotocephala transcriptome sequence, assembly, and validation through characterization of piwi homologs and stem cell progeny markers

“…The development of research tools to study gene expression and function in planarians, which include genome (Nishimura et al, 2015; Robb et al, 2015, 2008) and transcriptome (Brandl et al, 2016; Ishizuka et al, 2007; Nishimura et al, 2012; Sanchez Alvarado et al, 2002; Sasidharan et al, 2013; Zayas et al, 2005) sequences, as well as protocols for whole-mount in situ hybridization (King and Newmark, 2013; Pearson et al, 2009; Umesono et al, 1997) and RNA-interference (RNAi) (Newmark et al, 2003; Orii et al, 2003; Rouhana et al, 2013; Sanchez Alvarado and Newmark, 1999), have revitalized the use planarians as a model for molecular studies of stem cell-driven developmental processes (reviewed by Elliott and Sanchez Alvarado (2013), Newmark and Sanchez Alvarado (2002), Reddien and Sanchez Alvarado (2004), Rink (2013), Salo et al (2009) and Shibata et al (2010)). Planarians have also been the subject of recent work in toxicology, as well as behavioral, ecological, and evolutionary biology research (Alvarez-Presas et al, 2008; Hagstrom et al, 2016, 2015; Hicks et al, 2006; Inoue et al, 2015; Levin et al, 2016; Lombardo et al, 2011; Majdi et al, 2014; Shomrat and Levin, 2013), broadening their use as a model beyond fields related to developmental biology.…”

RNA interference by feeding in vitro–synthesized double‐stranded RNA to planarians: Methodology and dynamics

“…D. japonica P2X-A cDNA sequence inserted into pBluescript SK- (Nishimura et al, 2012; Sakurai et al, 2012; Shibata et al, 2012); DNA Data Bank of Japan accession no. FY959221) was used to amplify template for P2X-A dsRNA synthesis.…”