Molecular characterization of the apical organ of the anthozoan Nematostella vectensis.
Bottom Line: In bilaterians they are characterised by a tuft of long cilia and receptor cells and they are associated with groups of neurons, but their relatively low morphological complexity and dispersed phylogenetic distribution have left their evolutionary relationship unresolved.To provide a foundation for a better understanding of this structure we have characterised the molecular composition of the apical organ of the sea anemone Nematostella vectensis.Our study provides a molecular characterization of the apical organ of Nematostella and represents an informative tool for future studies addressing the development, function and evolutionary history of apical organ cells.
Affiliation: Sars Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt 55, 5008 Bergen, Norway.Show MeSH
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Mentions: The orthology search identified 73 putative sea urchin genes homologous to the genes in the Nematostella AO dataset, of which several have previously been shown to be expressed in the apical territory (e.g. frizzled 5/8, SFRP1, beta tubulin, foxJ1, Tektin (Croce et al., 2006a; Dunn et al., 2007; Illies et al., 2002; Poustka et al., 2007; Tu et al., 2006)). For an initial in situ hybridisation analysis 18 genes were selected for which no spatial expression data were available. Twelve of the 18 genes showed specific or enriched apical organ expression (Fig. 5 and Fig. S3) sometime during the developments of the sea urchin larva, while for the others no expression was detected (with the exception of one gene expressed in the gut, Aldh2). Of the genes with apical organ expression some were specifically expressed in the apical organ area (e.g. PACRG, Fig. 5C and D), while others had later additional domains in the ciliary band and few in the ciliated gut (e.g. Annexin, Fig. 5I and J). The gene for an acetylcholine receptor had a patchy ectodermal expression domain, with an enrichment of cells in the apical organ (Fig. S3).
Affiliation: Sars Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt 55, 5008 Bergen, Norway.