Cnidarians are an ancient group of animals at the base of metazoan evolution. They exhibit a simple body plan with only one well-defined body axis and a small number of cell types. Cnidarians are also well known for their enormous regeneration capacity. Recent work in the freshwater polypHydraand in the sea anemoneNematostellahas identified an unexpectedly high level of genetic complexity ofwntgenes. Canonical Wnt signaling acts in pattern formation and regeneration ofHydraand also in gastrulation and early embryogenesis ofNematostella. Vertebrate-specific Wnt-antagonists were also identified from cnidarians and exhibit similar conserved functions. The simple cnidarian body plan and the now available genomes fromHydraandNematostella, together with new functional approaches, make these animals an attractive model for studying the basic functions of canonical and non-canonical Wnt signaling.
