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Sponges are an ancient group of animals that diverged from other metazoans over 600 million years ago. Here we present the draft genome sequence of Amphimedon queenslandica, a demosponge from the Great Barrier Reef, and show that it is remarkably similar to other animal genomes in content, structure and organization. Comparative analysis enabled by the sequencing of the sponge genome reveals genomic events linked to the origin and early evolution of animals, including the appearance, expansion and diversification of pan-metazoan transcription factor, signalling pathway and structural genes. This diverse 'toolkit' of genes correlates with critical aspects of all metazoan body plans, and comprises cell cycle control and growth, development, somatic- and germ-cell specification, cell adhesion, innate immunity and allorecognition. Notably, many of the genes associated with the emergence of animals are also implicated in cancer, which arises from defects in basic processes associated with metazoan multicellularity.
The emergence of multicellular animals from single-celled ancestors over 600 million years ago required the evolution of mechanisms for coordinating cell division, growth, specialization, adhesion and death. Dysfunction of these mechanisms drives diseases such as cancers, in which social controls on multicellularity fail, and autoimmune disorders, in which distinctions between self and non-self are disrupted. The hallmarks of metazoan multicellularity are therefore intimately related to those of cancer1 and immunity2.
Sponges have a critical role in the search for the origins of metazoan multicellular processes3, as they are generally recognized as the oldest survivingmetazoan phyletic lineage. Although the kinship of sponges to other animals was recognized by the nineteenth century4, the absence of a gut and nervous system had relegated sponges to the 'Parazoa'5, a grade below the 'Eumetazoa' or 'true animals' (that is, cnidarians, ctenophores and bilaterians)6. Nevertheless, sponges share key adhesion and signalling genes7-11 with eumetazoans, as well as other genes important in body plan patterning such as developmental transcription factors12-15; sponge embryos and larvae (Fig. 1) are readily comparable to those of other animals12,16. Sponges are diverse and their phylogeny is poorly resolved17-19, allowing for the possibility that sponges are paraphyletic20, which implies that other animals evolved from sponge-like ancestors.
Here we report on the genome of Amphimedon queenslandica, a haploscleriddemosponge, the adult organization and lifestyle ofwhich is typical for sponges, feeding on microbes and...