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dc.contributor.authorWollesen, Tim
dc.contributor.authorRodríguez Monje, Sonia V
dc.contributor.authorTodt, Christiane
dc.contributor.authorDegnan, Bernard M
dc.contributor.authorWanninger, Andreas
dc.PublishedBMC Evolutionary Biology. 2015 Oct 28;15(1):231eng
dc.description.abstractBackground Mollusks represent the largest lophotrochozoan phylum and exhibit highly diverse body plans. Previous studies have demonstrated that transcription factors such as Pax genes play important roles during their development. Accordingly, in ecdysozoan and vertebrate model organisms, orthologs of Pax2/5/8 are among others involved in the formation of the midbrain/hindbrain boundary, the auditory/geosensory organ systems, and the excretory system. Methods Pax2/5/8 expression was investigated by in situ hybridization during the development of representatives of the two major molluscan subclades, Aculifera and Conchifera. Results Compared to the investigated polyplacophoran and bivalve species that lack larval statocysts as geosensory organs and elaborate central nervous systems (CNS), cephalopods possess highly centralized brains and statocysts. Pax2/5/8 is expressed in regions where sensory cells develop subsequently during ontogenesis. Expression domains include esthetes and the ampullary system in polyplacophorans as well as the eyes of cephalopods. No Pax2/5/8 expression was observed in the less centralized CNS of bivalve, polyplacophoran, and gastropod embryos, thus arguing for a loss of Pax2/5/8 involvement in CNS development in these lineages. In contrast, Pax2/5/8 is expressed among others in brain lobes along the trajectory of the esophagus that divides the cephalopod brain. Conclusions Our results, along with those on Otx- and Hox-gene expression, demonstrate that the cephalopod condition is similar to that in mouse and fruit fly, with Otx being expressed in the anterior-most brain region (except for the vertical lobe) and a Pax2/5/8 expression domain separating the Otx-domain from a Hox-gene-expressing posterior brain region. Thus, Pax2/5/8 appears to have been recruited independently into regionalization of non-homologous complex brains of organisms as different as squid, fruit fly, and mouse. In addition, Pax2/5/8 is expressed in multimodal sensory systems in mollusks such as the esthetes and the ampullary system of polyplacophorans as well as the eyes of cephalopods. Pax2/5/8-expressing cells are present in regions where the future sensory cells such as the polyplacophoran esthetes are situated and hence Pax2/5/8 expression probably predates sensory cell development during ontogeny. In mollusks, Pax2/5/8 is only expressed in derivatives of the ectoderm and hence an ancestral role in molluscan ectoderm differentiation is inferred.en_US
dc.publisherBioMed Centraleng
dc.rightsAttribution CC BY 4.0eng
dc.subjectSensory celleng
dc.titleAncestral role of Pax2/5/8 in molluscan brain and multimodal sensory system developmenteng
dc.typePeer revieweden_US
dc.typeJournal articleen_US
dc.rights.holderWollesen et al.eng
dc.subject.nsiVDP::Medisinske Fag: 700nob

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