Year: 2017
Type: preprint
Abstract: The major longitudinal body axis of cnidarians (e.g. sea anemones, corals, hydroids) is called the oral-aboral axis and in the anthozoan cnidarian Nematostella vectensis, this axis is established by the selective stabilization and nuclear localization of the protein Beta-catenin (a component of the canonical Wnt signaling pathway) in cells derived from the animal pole. These cells form the endomesoderm during gastrulation with the oral (anterior) pole forming at the animal pole. In bilaterian embryos the site of gastrulation occurs at the vegetal pole. We used a two-step experimental approach to mis-activate cWnt signaling in the developing cnidarian N. vectensis embryos by first erasing the endogenous oral-aboral axis by inhibiting the activation of cWnt signaling in the embryo and then, ectopically activating cWnt signaling at by blastomere injection at a site other than the animal pole. Using marker gene expression, we show that mis-activation of cWnt signaling in N. vectensis embryos result in a new oral-aboral axis. Our data show that the change in the site of gastrulation and endomesoderm specification is the result of moving localized components of the Wnt signaling pathways to the vegetal pole in the last common ancestor of all bilaterians, thus, providing a plausible mechanism for the change in the site of gastrulation from the animal pole in non-bilaterians to the vegetal pole in bilaterians. This change in the metazoan developmental program is arguably the largest developmental constraint in animal evolution as it restricts endomesodermal fates and neural fates to opposite poles of the embryo and paved the way for the rapid diversification (e.g. cephalization and mesoderm formation) of the bilaterian body plans.
DOI: 10.1101/220988
Authors: Naveen Wijesena, Mark Q. Martindale
Institutions: University of Florida, Rajarata University of Sri Lanka
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2768898332