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FGF signalling controls formation of the apical sensory organ in the cnidarian Nematostella vectensis
Jens H. Fritzenwanker1,
Corinna B. Scholz2, and
1 Sars Centre for Marine Molecular Biology, University of Bergen, N-5008 Bergen,
Norway. 2 Miltenyi Biotec, Friedrich-Ebert-Str. 68, 51429 Bergisch-Gladbach,
Germany. 3 Faculty of Life Sciences, University of Vienna, Althanstrasse 14, 1090 Wien,
Authors for correspondence (e-mails:
Accepted for publication 12 March 2008.
Fibroblast growth factor (FGF) signalling regulates essentialdevelopmental
processes in vertebrates and invertebrates, butits role during early metazoan
evolution remains obscure. Here,we analyse the function of FGF signalling in
a non-bilateriananimal, the sea anemone Nematostella vectensis. We
identifiedthe complete set of FGF ligands and FGF receptors, of whichtwo
paralogous FGFs (NvFGFa1 and NvFGFa2) and one FGF receptor
(NvFGFRa)are specifically coexpressed in the developing apical
organ,a sensory structure located at the aboral pole of ciliated larvaefrom
various phyla. Morpholino-mediated knockdown experimentsreveal that NvFGFa1
and NvFGFRa are required for the formationof the apical organ, whereas
NvFGFa2 counteracts NvFGFRa signallingto prevent precocious and ectopic
apical organ development.Marker gene expression analysis shows that FGF
signalling regulateslocal patterning in the aboral region. Furthermore,
NvFGFa1activates its own expression and that of the antagonistic
NvFGFa2,thereby establishing positive- and negative-feedback loops.
Finally,we show that loss of the apical organ upon NvFGFa1 knockdown
blocksmetamorphosis into polyps. We propose that the control of the
developmentof sensory structures at the apical pole of ciliated larvaeis an
ancestral function of FGF signalling.