Wnt and TGF-β Expression in the Sponge Amphimedon queenslandica and the Origin of Metazoan Embryonic Patterning

Abstract

We infer from the expression of Wnt and TGF-beta in Amphimedon that the ancestor that gave rise to sponges, cnidarians and bilaterians had already evolved the capacity to direct the formation of relatively sophisticated body plans, with axes and tissues. The radially symmetrical expression patterns of Wnt and TGF-beta along the anterior-posterior axis of sponge embryos and larvae suggest that these signalling pathways contributed to establishing axial polarity in the very first metazoans.