Components of TGF-beta signaling pathway in the sponge Halisarca dujardini.

Abstract

International audienceTGF-beta pathway is one of the major signaling mechanisms that orchestrate development of multicellular organisms. Axial patterning in embryo development is the brightest example of its role. Thus, asymmetric expression of TGF-betasuperfamily ligands determines of dorso-ventral axis in bilateral animals. Ligands from several families manage the different embryonic morphogenesis through regulation of proliferation, differentiation, apoptosis, cytoskeleton, adhesion and cell migration. Functions of TGF-beta pathway established early in evolution of multicellularity as ligands or receptors not found in Protista, whereas in Cnidaria this pathway determines the directive axis of body. At the same time, TGF-beta expression data from sponges’ development tell us about involvement of TGF-beta pathway in axialpatterning of Porifera embryo. Number of ligands may be as many as eight in demosponge Amphimedon queenslandica or twenty-two in calcisponge Sycon ciliatum so sponges are not simple in sense of ligand repertoire in comparison to Bilateria. In this study we search through transcriptome and analyze ligands, receptors and cytoplasmic messenger proteins of TGF-beta pathway in sponge Halisarca dujardini (Demospongiae). Eight ligand sequences wereidentified, and their primary structure and domain organization correspond to eumetazoan TGF-beta. Three of eight identified ligands can be classified as TGF-beta sensu stricto when next five are not fall into any of eumetazoan family of TGF-beta. With hybridization in situ and quantitative transcriptomics shown that expression of some ligands restricted to oscular tube similar to Wnt expression pattern. Similar situation described for Wnt pathway ligandsin sponges, and it shows independent involvement end lineage-specific expansion of some signaling pathways members inside Porifera phyla