Cnidarian-bilaterian comparison reveals the ancestral regulatory logic of the β-catenin dependent axial patterning

In animals, body axis patterning is based on the concentration-dependent interpretation of graded morphogen signals, which enables correct positioning of the anatomical structures. The most ancient axis patterning system acting across animal phyla relies on beta -catenin signaling, which directs gastrulation, and patterns the main body axis. However, within Bilateria, the patterning logic varies significantly between protostomes and deuterostomes. To deduce the ancestral principles of beta -catenin-dependent axial patterning, we investigate the oral-aboral axis patterning in the sea anemone Nematostella-a member of the bilaterian sister group Cnidaria. Here we elucidate the regulatory logic by which more orally expressed beta -catenin targets repress more aborally expressed beta -catenin targets, and progressively restrict the initially global, maternally provided aboral identity. Similar regulatory logic of beta -catenin-dependent patterning in Nematostella and deuterostomes suggests a common evolutionary origin of these processes and the equivalence of the cnidarian oral-aboral and the bilaterian posterior-anterior body axes. The authors show in Nematostella that the more orally expressed beta -catenin targets repress the more aborally expressed beta -catenin targets, thus patterning the oral-aboral axis. This likely represents the common mechanism of beta -catenin-dependent axial patterning shared by Cnidaria and Bilateria.

Automated summary

Animals rely on concentration-dependent interpretation of morphogen signals for body axis patterning, while the ancient axis patterning system across animal phyla involves beta-catenin signaling. Differences in patterning logic exist between protostomes and deuterostomes, but a common regulatory logic of beta-catenin-dependent patterning is observed in Nematostella and deuterostomes. This suggests a shared evolutionary origin of these processes and the equivalence of cnidarian oral-aboral and bilaterian posterior-anterior body axes.