| Recent molecular analyses suggest the cnidarians (corals, sea anemones, and "jellyfish") may be the sister group to the bilaterians, yet traditionally, cnidarians are classified as lacking the synapomorphies that unite the Bilateria (triploblasty, bilateral symmetry, and a centralized nervous system (CNS)). Cnidarians belong to a group of organisms commonly referred to as the Radiata, and are diploblastic (lacking mesoderm), radially symmetric, and lack a CNS, possessing a diffuse nerve net instead. The genome of N. vectensis , the starlet sea anemone, an anthozoan cnidarian, has been sequenced, and represents the first publicly available non-bilaterian, metazoan genome, providing a unique opportunity to investigate the molecular basis for body plan evolution outside of the Bilateria. Utilizing the available N. vectensis genome sequence, I have isolated and characterized the spatial and temporal expression of many of the developmental regulatory and signaling pathway genes that have been implicated in establishing germ layer identity, symmetry properties, and nervous system organization in bilaterians, including members of the Transforming Growth Factor beta (TGFbeta) pathway, their antagonists, the Pax family of transcription factors, and the Fibroblast Growth Factor pathway (FGF). Expression data suggests that N. vectensis utilizes these conserved signaling pathways to establish germ layer identity and a bilaterally symmetric body plan at the molecular level, and possibly organize a regionalized nervous system, suggesting that the ancestor of cnidarians and bilaterians may have been much more complicated that previously thought. |
